I believe the best way to get all user actions (and any RUM info) would be the USQL API endpoint. USQL is a SQL-like query language that lets you get all the info related to your user sessions.
Here is USQL documentation: https://www.dynatrace.com/support/help/how-to-use-dynatrace/real-user-monitoring/how-to-use-real-use...
And here's the API documentation for USQL: https://www.dynatrace.com/support/help/dynatrace-api/environment-api/user-sessions/
Here is a USQL statement that can achieve grabbing the user actions for you:
I actually just ran into this myself yesterday, props to James Kitson for building this query!