Did you not know?
You can simply select all files you want to commit, in the File Manager, Ctrl+C, then paste in the terminal and it will automatically add all those file names (full paths) separated with spaces at the cursor. At least in KDE: Dolphin -> zsh + Konsole it does.

And sure, it might look like 2 extra steps, but you will still be clicking around a lot in case of a GUI anyway.

I tend to just type partial filenames and use tab completions, which are also pretty configurable. And the only dissatisfaction I have rn, is that I don't have zsh module for completions with pascal case and snake case.