In 2002 I released a little GNOME app to rename files by changing the start or end of the filename, using gtkmm and gnome-vfs(mm). It worked well enough and was even packaged for distros for a while before the dependencies became too awkward.
I’ve never heard of a single person using it, but I still need the app now and then so I just updated it and put it in github, changing it from gtkmm 2.4 to gtkmm 3, removing the bakery dependency, and changing from gnome-vfs to GIO. I also removed most signs of my 2002 code style.
It seems to work, but it really needs a set of test cases.
I’m sure that the performance could be vastly improved but I’m not greatly interested in that so far. Patches are welcome. In particular, I haven’t found an equivalent for the gnome_vfs_xfer_uri_list() function for renaming several files at once and I guess that repeated sequential calls to g_file_set_display_name_async() are probably not ideal.