As I mentioned on reddit (https://www.reddit.com/r/kde/comments/k71i6n/this_week_in_kde_big_new_accentedalternative/gepr2x6/), perhaps the palette could be expanded and with it also its keyboard navigation:

*When the popup is opened, only 10 options plus a ··· below them are shown.

*The ··· serves the purpose of indicating you have more options than what is displayed.

*If you type any arrow key, the popup expands, the ··· disappears, and you get a wider array of characters to choose from.

*Arrow keys thus allow to navigate between/highlight each option. They coexist with the current setup that activates an option with numbers.

*To activate a character, press Enter after having highlighted it with the arrow keys or click on it with the mouse.

This would remove the limitation of 10 characters while keeping them as a non-cluttered default.