In some ancient version of the Mac OS, I seem to recall that, while in a "Save" dialog, there was a way (or an extension which provided a way) to click on an open folder in the Finder in order to specify that directory as the save target. Does that functionality still exist?
Context: I needed to save a new AppleScript (using Script Editor) into the ~/Library/Scripts directory and could not find a way to do it without manually navigating to the directory through multiple clicks. The dropdown menu in the "Save" dialog did not list the directory because I had not saved to it recently. The directory was open right next to the editor. I know about the accelerators to navigate to the top level directories but those don't help in this case.
Best Answer
The specific software you are probably alluding to is Default Folder X - which even allows you to click through any intervening windows to return to a folder visibly open on the Finder desktop. It also has a pre-determined list of 'useful' places & a history list. I do consider it one of the indispensible utilities on Mac.
Alternatively, macOS itself allows you to drag any visible folder onto a file-picker dialog to send the dialog to that location.
Fullscreen apps may interrupt either of those efforts - but I have a particular set of reasons I absolutely never use fullscreen, so I'm not certain how it will respond.