With the chains function, you can "chain" several plugins together.
Fi:
You first apply gain, then eq, then compression. You do this once only, with 3 separate functions or plugins. Once you've done that, you save it as a chain. Next time, you apply the chain to the audio and it will apply all saved presets for every function/plugin with one command in one go. Especially useful if you need to treat a large number of files in the same manner.
And, yes, I mean the "official" forum, of course. This one:
Audacity Forum • Index page
There's some confusion with Audacity's links. That's because Sourceforge, their previous code host, decided to go into adware a couple of years ago. So the team had to move to other hosts in a hurry. Unfortunately, a lot of the old links still live on. When you google for Audacity features, you'll encounter more goofs than results. And a number of years ago, the old Audacity team stopped developing it. A new, dynamic team has taken over since, but the heritage of the previous developers still lingers on on the net.
But it's a great editor.
REAPER doesn't have those problems, because everything circles around one, well maintained forum.
REAPER's problem is that it can do anything. And it will do most things much better than any other DAW.
But for finding out how to do some of these things, you need to ask on the forum and wait for someone to point you to the right workflow. And sometimes, you are the first one to ask for this workflow, so you need to wait for one of the marvelous scripters to pick up and resolve your problem. It's fantastic, but you need basic audio knowledge, persistence and patience. It's a bit less suited for beginners.