Not sure if this helps…
Here are my two addons that will be backed-up:
[root@ipfire ~]# ls -al /var/ipfire/backup/addons/includes
total 16
drwxr-xr-x 2 root root 4096 Jan 10 22:42 .
drwxr-xr-x 4 root root 4096 Dec 22 19:23 ..
-rw-r--r-- 1 root root 31 Dec 18 04:52 netatalk
-rw-r--r-- 1 root root 19 Dec 18 05:24 transmission
Each file includes a list of files for backup.
FYI - I don’t recommend adding your own files manually. I don’t know what might happen…