Here is Sequence FM v.4. Code is now a lot cleaner and minimized to (about) 189 lines. In this release I placed resources under their own respected menus and also made right-click menu layout clearer.
Also, a notable change happened to copy, paste, move and delete functionalities. The previous now have their own program: Gtk-Tools, which is dedicated to handle those actions. Gtk-Tools is made out of the old Crosslinker FM code and thus it might seem familiar.