In ~/.config/rosegardenmusic/Rosegarden.conf
Start Rosegarden.
File > Open
Confirm that the dialog is in your home directory or someplace else sensible for a first launch.
Open a file in a directory other than ~ or your build directory or the current directory when running rg.
File > Open
Confirm that the open dialog is in the directory from the last open.
In the dialog type a name that doesn't exist and hit return.
Confirm “Cannot open file” dialog.
Click OK.
In Rosegarden.conf, confirm [Last_Used_Paths] open_file is the directory of the file that was opened (not just a dot “.”).
File > Open
Confirm that the open dialog is in the directory from the last open.