What you are after is possible already considering I understood corectly.
You can set the FSMOwner’s option on the inspector to “Do Nothing” OnEnable.
Then at any given moment you start the FSM using:
FSMOwner.StartBehaviour(); (or any overload of that).
The FSM will start, traverse the transitions based on the conditions and as soon as it reaches a finished node without any outgoing transitions the FSM will automaticaly stop.
Is that what you are after, or something you tried but it’s not what you are after?