Just wanted to chime in here - My particle actions are also not appearing in the action browser. I checked to see if I'd somehow not installed a package, checked on ecosystem, nothing. This is a new project I'm working with, but I use these actions all the time, and was very confused until I found this post.
I'm running in Unity 2019.4.26, with Playmaker v1.9.0p21 in Win8.1. Thank you for uploading the package in the meantime, but maybe there's something there that bears investigation.