Neither in Firefox nor in the Windows desktop app.
When accessing the panel, either manually or with the shortcut "f," you can't type it directly; you have to click inside the box.
Regarding this bug, I'd like to take this opportunity to point out that it's annoying not being able to use a capital "F" like other program shortcuts, which do allow it. Report it here.
This report is also related and truly unproductive.
Thanks.