Excel cursor

Open Excel.

Go to File - Options.

Click Advanced on the left.

On the right, in the Editing Options section, enable this setting 'Enable fill handle and cell drag and drop'

Then click OK to apply the setting.

In Excel, the mouse pointer changes shape depending on where it is and what action is available. A plus sign is normal in some cases:

• Over the worksheet grid (select cell): white plus (selection cursor)
• Over the fill handle (bottom-right corner of a cell): thin black plus (fill handle cursor)

To “change it back,” move the mouse slightly:

• Move off the fill handle (bottom-right corner of the active cell) so the pointer leaves the thin black plus and returns to the normal white plus or arrow.
• If the cursor looks wrong everywhere in Windows (not just Excel), adjust it in Windows settings: Settings → Accessibility → Mouse pointer and touch, then change style/size to something easier to see.

If the cursor is flickering or behaving oddly after a Windows/Office update, make sure Windows and Office are fully updated, as cursor issues in Excel have been fixed by updates.

References:

• Excel cursor flickers after updating to Windows 10 Fall Creators Update (v1709)
• Application.Cursor property (Excel)
• _Application.Cursor Property
• how do i make the cursor larger and darker? - Microsoft Q&A