The modal versus non-modal issue, plus the Windows hi-lite issue, may partly explain the current design. It is actually quite usable once understood. The problem is that the current sparse doc does not adequately explain the intention - use ^F once to set the key and find it once, use ^G to find again.

It might help if the Find box itself had a reminder. "Use <bound key> to find the text again after this box closes." I suspect I read and understood the use of ^G once (years ago) and just forgot it due to disuse.

I do not think we should change the current design without more thought and discussion*. The current behavior is intended and not a bug. I suspect that there are people who have learned it and use it as is. 

For Notepad++ on Windows, the model search window goes somewhat transparent when one shifts focus to the edit window by clicking on it. However, one must either do this or click [close] on the dialog in order to edit.  One can 'find next' either by clicking the Find Next button *or* (when the dialog is closed) by hitting the key bound to find-next. Having to explicitly close the window to edit is a trade-off. It makes it easier to find - find- find without editing. It makes it a bit harder to actually edit after find (an extra action).

The one search thing I do constantly in Notepad++ that is more painful is finding all occurrences in the current file. Find in Files defaults to *.py in the current directory, so one has to replace '*' with the current file name. There should be a Find All button in the Find box (like Notepad++) or a Current File button in the Find in Files box.

*Another issue: The addition of Cut Copy Paste to the *top* of the right-click context menu for the Find in Files *Output* window is a nuisance. It makes it much harder to jump to the file and line of each entry as one now has to slide the mouse much further to get to the 
'Go to file/line' entry. I think this should be changed. My point for this issue is that changing features requires thinking about more than just one behavior or use in isolation.