Hi,
That's nothing to do with PlayMaker. It's unity that compiles your project again. It's a pain indeed... and it happens when your project starts to be big.
The actual search for all actions in a project is very fast, this is not the issue here.
if you create a new behavior, the compiler will do the same job as if you create a custom action, no difference for Unity nor playmaker.
Maybe there is a way, but it's been mentionned many times that the compiler needs to be optimized to recompile only what really needs it, and so far I think it's far from being the case indeed...
Bye,
Jean