The flowlab "what's this?" Users guide states the following about the Once Trigger:
"""Reset on Level Start
When on, this trigger will be reset when the game level is restarted. When off, this trigger will only fire once, even if the level is restarted.This optional property is only available when object containing the behavior is set to keep on level restart or keep between levels.
However I have found this not to be the case. I have GUI layer object in a platform game I am working on that is suppose to be the life counter. I have it configured to "Keep between levels" in the objects "edit game object" menu, once triggers in this objects behavior space show the "reset on level start" config option as expected and it is not selected. However I confirmed that this once trigger does in fact fire after the level restarts.
I have also tried changing the objects config from "Keep between levels" to "Keep on level restart". I have tried using a "restart game" and a "next level -> restart current" in both object configurations. In all cases I have confirmed the once trigger fires when my level restarts. It appears this feature is completely non-functional. Which is unfortunate because it would be a great way to implement a life counter and Flowlab is otherwise pretty great for platform games.
I hope they fix this because the work around I developed for a life counter is extremely messy.
Here is a link to try yourself, press "d" to walk forward in to the pit and die.https://flowlab.io/game/view/1170810