You can simply tell it to use Private_media/media/immich as a target. If it doesn’t exist yet it will be created automatically and properly set/inherit it’s properties.
Then when you include more datasets in the source for this single replication task like this: Private_media/configs/immich,Private_media/configs/whatever you change the destination back to Private_media/media and since there’s now multiple sources it’ll use the last section of each source as a target.
So immich still goes to Private_media/media/immich and whatever would target Private_media/media/whatever.
Or if you want multiple independent jobs just set the Private_media/configs/whatelse → Private_media/media/whatelse source/destination on each of them. The location you specify will be created automatically.