An "action" is a term of art that basically means a lawsuit with a particular case number.
Claims for relief within a single lawsuit with a single case number are not "actions" (even if none of the parties to the different claims overlap).
It isn't unheard of for there to be multiple civil actions pending at the same time regarding overlapping subject matter. But this is risky, because the first one to "final judgment" (something that has quite a technical definition) has "res judicata" effect that could be grounds for dismissal or summary resolution of all of the other lawsuits.
To prevent this from happening, the other side facing multiple lawsuits can move to consolidate all of them into one case (there are a couple of different way this happens depending on the procedural details).
Stays of one action by a judge knowing that other actions are pending are possible, but usually reserved for situations when motions to consolidate are pending.