When editing a formula in Google Sheets, how do I resume 'range selection mode' so that I can select a range with the mouse or keyboard?

Question

When you first enter a formula in Sheets you can use the mouse or cursor to select the range. If I want to sum the 5 cells below the cell with the formula, I just type =SUM( and then use the down arrow and shift key to select those 5 cells. However, as of maybe 3 weeks ago, you cannot use this range selection mode when you edit an existing cell formula. The only way to change a range in an existing formula is to manually type in the range (e.g., {B5:B10}). This makes it extremely difficult or impossible to work with long formulas. Google's help center says,

• When editing a formula, the range-selection signal (a grey bracket) will appear next to your cursor where you’re likely to need a range in the formula. When you see the signal, you can move the keyboard arrows around your sheet to select a range.
• Toggle this mode on and off using the keyboard shortcuts F2 or Ctrl + E. If range-selection mode is turned off, use the arrow keys to move your cursor inside the input box instead of selecting a range.

But this does not work for me (on Mac, and have tried many permutations such as SHIFT+F2, SHIFT+CTRL, etc etc). This feels like a bug to me but asking here in case there's some undocumented method.

Answer 1

When post-editing the formula the trick is to trigger the underscore:

as soon as you do you are instantly able to create a selection with your mouse (in some cases even with keyboard). So, for example, if you wish to edit the range by selection you will need to delete it (the range) in order to again trigger the underscore.