Thanks, @Girton. Thankfully, this got put on the back burner for right now, but I'm sure I'm going to start getting pressured for it again soon, so any help is definitely appreciated.
Unfortunately, I think I'm already doing what you are suggesting. The first step of the workflow is to find and define a Snapmirror relationship based on a given volume name that the user enters:
Then, it will wait until any running Snapmirrors are finished before continuing on. This part works as long as I don't have a condition in the Advanced tab. So, I know it's defining it correctly. It will even let me use the dropdowns to create the condition (see screenshot), I'm just not sure what the syntax is after defining the parameter I want to look at to judge the condition. Is snapmirror1.volume.state == 'online' the correct syntax? I only want it to wait for the Snapmirror update to complete if the source volume is online.