Are there any settings or policy in bigfix for purging data (e.g. actions) over a specific period of time?
To put it clearly, No! Nothing in BigFix by default allows you to schedule or automatically remove actions.
However, the Audit Trail Cleaner automatically removes the operator’s deleted actions from the database.
Many organizations use out of box custom solutions that automatically remove actions based on specified criteria; some use a direct database approach (not recommended), while others use REST API for cleanup.
You can explore below fixlet:
https://www.bigfix.me/fixlet/details/3754