I normally use the mouse, but just tried ⇧⌘F to refocus the Find
window and it preserved the selected folder. That makes sense to me
since ⌘F is supposed to be limited to a single document or selection,
while ⇧⌘F is for searching something larger like “in folder”.
I use ⇧⌘F for this purpose all the time and find it convenient.
However, there is a strange issue when you are working with multiple projects open.
1. Bring project1 to the front. Press ⇧⌘F and search in that project. The search window will have a list of matches in project1.
2. Bring project2 to the front (perhaps to make a quick edit).
3. Press ⇧⌘F to bring the search window to the front again. Click on one of the matches that are still in the search window from before.
4. The file with the match is opened as a tab in project2 rather than project1.
Not a big deal but can catch you of guard if you are not expecting it.