Turns out that if you open a certain folder often enough that it will add a shortcut to that location above the "Home", "Desktop", and "Documents" icons.
I still don't know if there's an option somewhere to manually add frequently opened locations to the File Open (Ctrl-O) dialogue window or what if you wanted to edit which shortcuts you have available there in a case where maybe you have multiple folders you open files from often. Sounds like a quality of life improvement opportunity for the developers of the software.