Custom audit actions (outside of update/create/delete) do not work well in foreman for a couple reasons:

1) the UI assumes all action names can be appended with the letter 'd' to form a past tense form
2) the search on actions only allows searching and auto-complete for those 3 specific actions

In addition there is a mismatch for the action you can search for and what is displayed on the audits list.
There is also a mismatch with the api.