Is there a way to run an MS flow (Named X) that we've created separate of our PowerApps?
I think, one way of doing it would be to create another Flow (B) that would then run X, but is there an easier way? For examole, there is an MS Flow connecter in PowerApps, but I could not figure out if it can be used to run external Flows.
Yes, you can. The only drawback is that before you can do that you have to remove all the references to the trigger in other places in your Flow. As long as output of the trigger is used elsewhere in the Flow the option to delete the trigger is grayed out.