Google Sheets: how can I switch from enter to edit mode when I'm entering data in a cell, so that I can use arrow keys to change something I've typed?

When I first type data into a cell in Google sheets, I can use Home, End and Backspace to edit what I've typed.

However, I cannot use the arrow keys to move within the text I've typed - they "enter" the data and move the focus to another cell.

If I mouse-click in the cell, then the mode changes from "Enter" to "Edit" mode, and I can use the arrow keys to edit the cell text.

Is there a way to switch from "Enter" to "Edit" mode using the keyboard?I've tried: F2 (does nothing), Shift-Enter, Enter (leave the cell)