Hi,
I've been on the same boat as you for some months now.
There's no built in Spine support in core PlayMaker, nor in its Ecosystem (community provided actions), as seen here...:
Also, the only asset that added custom actions was pulled off the Asset Store because it became incompatible and its author didn't updated it. Mind that Spine is constantly evolving and its Unity Runtimes are also bound to change, messing up those custom actions in the process.
So whoever want to have Spine support would need to change those scripts from time to time, which is a catch 22 situation as most people who use PlayMaker have little or no programming experience (my own case), while programmers wouldn't see a reason for spending time updating action scripts for a plugin that they don't need nor want.
So in short, we're screwed. :p
I'm sure you've found these here...: PLAYMAKER Integration
...but the only actions I've been able to salvage as valid are 'Animation' and 'Slot' actions, and I still needed to modify the first to serve my purposes. And it's not pretty code, I assure you. :$
I'm attaching it anyway, just in case you find it useful...
Maybe I'll spend some more time tinkering with this in the (far) future, but I'm not particularly knowledgeable in C# and I don't need more than this for the time being.
Cheers.