I answered my own question by finding the samples page on GitHub and looking at the Groups one for reference.
Hope this helps someone else equally new to this stuff.
Did you ever try and get the memberDefinitions parameter in too, im struggling to get that in. I can do it manually via the SWIS Studio but not in my script
Sorry for the months-late response.
I eventually did, but it's clunky and kind of a pain since it just creates a bare-bones dynamic query. I'll upload what I've got now and link you. Also I'm cringing hard at my old script, so it's pretty cool to see some progress.
Just kidding, content exchange appears to be broken today. Here's what I did, hope this helps or that you already got it working:
Invoke-SwisVerb $swis "Orion.Container" "AddDefinition" @(
#-----------Dynamic Query Below
#----------End of Dynamic Query
) | Out-Null