For example, I post threads out to our social media sites using the main RSS feed but this includes our welcome forum, support forum, off-topic forum, etc. It would be great if I could create a custom RSS feed without those forums.
Another example. My pets forum has busy dog and cat sections. It would be great if I could create a 'Dogs' RSS feed that only featured the forums in the dogs category. The same for cats.
For CycleChat I could split road, MTB, commuting, folders, vintage, etc.
So ... login to the ACP, navigate to the custom RSS section, create a new feed, name it, select the forum nodes, and publish. Bish, bash, bosh!