Is there a reason why Dopus does not associate itself with .ocb files? Doing so on install would simplify life a bit
Every extension we take over adds the potential that some other program also uses the same extension and we cause a conflict by taking it over. So we only do it where it seems really useful.
Importing a config isn't something many people do often, and it only takes a couple of mouse-clicks to do via Settings -> Backup & Restore, so it doesn't seem worth taking over the filetype.
It's possible to create the filetype/association manually if you wanted to (e.g. so double-clicking a .ocb imported it). But if you're importing different configs that often there's probably an even easier way to do whatever it is you're doing it for.
For myself, I've taken to assigning .dis, .dlt, .dps, and .ocb to the list of Zip Extensions in Prefs in order for Opus to treat them as zip files. I've also then created an Archives.Opus File Type Group, to which I've added those same extensions, and assigned various go commands to the mouse click Events... and then finally, a Context Menu action that runs:
recent clear
prefs backuprestore restore=all,replace from {f}
...to restore an OCB backup.
It's trivial to add this stuff to Opus, though if you then restore an OLDER config backup made from before you add such changes then you'll naturally have to make the changes all over again .