Excel Beta Adds In-Cell Arrays and Lists: #SPILL! Fixes, Compatibility Risks and iPad Copilot

Neowin says the iPad feature is generally available and the rest are Insider-only. Microsoft's own documentation is more careful about the iPad feature than that, as covered below.

The big one: multiple values in a single cell​

Microsoft put this plainly in its announcement: "Throughout Excel's 40-year history, you've only been able to put one value per cell." The company says that is changing with the release of lists, arrays in cells, and nested arrays, initially to Microsoft Excel for Windows and Mac Beta Channels. Microsoft's Microsoft 365 Insider blog announced the change on September 24, 2026.

The update has three parts:

• Lists. Users create one through Insert > List or with the Ctrl+J shortcut, then type items separated by commas or semicolons, depending on regional settings. The values stay grouped in one cell, but Excel treats them as separate items instead of one text string. Microsoft's example is a project with three owners, or a survey answer containing several time slots. With lists, you can keep those values in one cell, while also keeping them separate for filtering, calculation and more.
• Arrays in cells. A formula such as ={1;2;3} normally spills into three worksheet cells. Wrapping the formula body in braces keeps the output inside one cell instead.
• Nested arrays. Nested arrays previously produced a shortened result or a #CALC! error. Microsoft says supported formulas now return the full nested result, which stays available for later calculations.

A #SPILL! fix for table users​

The most useful everyday trick may be one that Excel Campus highlighted. Normally when you use FILTER inside an Excel Table, you get a cascade of #SPILL! errors because the formula tries to spill into rows below it that are occupied. Wrapping the whole formula in curly braces tells Excel to collapse the results into a single list in a cell instead of spilling down. If you've been gluing results together with TEXTJOIN to avoid spill errors, this could replace that workaround.

Microsoft's own demo is a running log. Each row stores an array of split times, so runs with different numbers of splits sit in the same table while Excel still calculates total time, average split, average speed, and fastest kilometer. Variable-length data in one tidy table used to be exactly the job people handed over to Power Query or a database.

The four new functions​

A few details on how FLATTEN works. Excel Campus explains that the optional pad_value is a value used to fill structural gaps when arrays at different levels have different widths, and that levels defaults to flattening all levels. In Microsoft's example, an empty string ("") for pad_value leaves blanks for rows with fewer items. My Online Training Hub adds that FLATTEN's results can spill into cells or pass directly into another function such as SORT, UNIQUE or COUNTIF.

Before you rush in: preview caveats​

Microsoft is clear that this is not ready for production. These are preview features. Their behavior may change before general release based on your feedback. We don't recommend using them in important workbooks until they're generally available.

There is also a compatibility issue that matters to anyone who shares files. Microsoft says Compatibility Version 3 will be released alongside arrays in cells and is required for most calculations involving nested arrays. Microsoft's announcement says the setting is chosen per workbook under Formula > Calculation Options. It also warns that some existing formulas return different results under Version 3, and that users whose workbooks misbehave can stay on Version 1 or 2.

Office Watch notes another current limit: lists can't feed a dropdown yet. gHacks confirms that the feature is opt-in and currently limited to Microsoft 365 Insiders in the Excel Beta Channel on Windows and Mac.

Section summary: This is the biggest change to Excel's data model since dynamic arrays. For now it belongs in test workbooks on Beta Channel builds, not in the quarterly finance model everyone else opens.

Naming a table as you create it​

This change is smaller but welcome. Neowin reports that when you insert a table, you can now give it a name straight away instead of accepting "Table1." Excel trainer Chris Menard describes the name field as part of the Create Table dialog. He reported it rolling out to the Beta Channel as of August 30, 2026, so it may have reached some Insiders before Neowin's September roundup. I didn't find a Microsoft announcement confirming the exact interface or rollout status, so treat those details as reported rather than officially documented.

Why should you care? Compare =SUM(Table1[Column3]) with =SUM(Sales_2025[Revenue]), the example Menard uses. Descriptive names make structured references readable, make the Name Box a useful way to jump around the workbook, and make Power Query and data models much easier to trace.

If you're not on the Beta Channel, you can already rename a table in any current version of Excel:

1. Click anywhere inside the table.
2. Open the Table Design tab (just Table in some versions).
3. Find the Table Name box on the far left.
4. Type a new name and press Enter.

Menard also argues that clearer table names help Copilot understand prompts. That seems plausible, but it is his view, not something Microsoft has documented.

Center Across Selection moves into the Merge & Center menu​

Neowin reports that Microsoft has added Center Across Selection to the Merge & Center drop-down for Windows and Mac Insiders. The change is tagged "#FIA", which Neowin says means Microsoft acted on customer feedback. I couldn't find a primary Microsoft note confirming this change, so it's attributed to Neowin here.

The option itself isn't new. It has long been in the Format Cells alignment settings, where plenty of users never go looking. It centers text across a selected range without merging the cells. Merged cells are notorious for breaking sorting, selecting, copying and filtering. Putting the better option right next to the one that causes trouble is a small UI change that could spare a lot of people from unmerging a spreadsheet by hand.

Excel for iPad gets Copilot editing, with a caveat​

Neowin reports that Excel for iPad now has the Copilot editing experience already on Windows. You can use natural-language prompts to transform data, build visuals and pull out insights, and Neowin describes the feature as generally available.

Microsoft's support documentation is more cautious. Its "Get started with Copilot in Excel" page lists chat and plan modes on iPad, and says edit mode support is rolling out to production. The Copilot FAQ uses the same wording. So some iPad users may not see edit mode yet. The iPhone is also listed as getting edit mode, and Android is chat-only for now.

Some context on the three modes Microsoft describes:

• Edit mode: Copilot changes the workbook directly.
• Plan mode: Copilot proposes an approach for you to review before it edits anything.
• Chat mode: Copilot analyzes the workbook and answers in the pane without changing it.

Microsoft's FAQ includes some caveats worth knowing before you let an AI edit a shared workbook:

• Copilot editing is supported only when Calculation Options are set to Automatic.
• Saved changes are visible to everyone with access to the file, including people coauthoring with you. Undo and version history are your safety net.
• Microsoft warns that results can be inaccurate, and advises against using Copilot for sensitive finance, legal or medical decisions.
• Access depends on your license, app version, network and, for business accounts, how your organization's tenant is configured.

For IT admins: Microsoft says Copilot in Excel is part of Copilot Chat and can't be turned off separately. The existing Copilot Chat access controls apply.

Analysis: a month that's mostly not about AI​

Neowin called it a nice change of pace to see Microsoft focus on something other than Copilot. That's fair. Three of the four items are improvements to the spreadsheet itself, and the headline feature changes a basic rule of how Excel works. Only one item is an AI rollout.

There is a real tension here. In-cell arrays are powerful, but they add a new workbook compatibility layer. Anyone who lived through dynamic arrays showing up as @ signs or legacy CSE formulas in older Excel builds will know what happens when a colleague on an older build opens a newer workbook. The practical advice is simple:

1. Test only on copies while features are in the Beta Channel.
2. Check the compatibility version of any workbook before relying on nested-array results.
3. Hold off on sharing list-based workbooks with people outside the Insider program until Microsoft ships these features broadly.
4. Check the Copilot mode picker on iPad instead of assuming edit mode has arrived.

If Microsoft gets the rollout right, lists in cells could remove a lot of the TEXTJOIN hacks, helper columns and spill errors that heavy Excel users have learned to live with.