Just thinking out loud …
Actions are not executed in a Curved Turn mission because the drone never reaches the Waypoint … makes sense. The “trigger” that disables Actions must be pulled when Path Mode is set for Curved Turns. Could Litchi “fix” Waypoint Mission Settings so that you could set Path Mode to Curved Turns and Default Curve Size to Zero% without disabling Actions? You could then set a Curve Size at each individual Waypoint. If you wanted a nice curve and no Actions at a particular waypoint, you’d simply enter a Curve Size number greater than zero for that Waypoint. If you wanted to execute some Action at another Waypoint, you’d set Curve SIze to Zero in that Waypoint Settings dialog box. Wouldn’t the drone then reach the Waypoint, and couldn’t the Actions then be executed? (No, I don’t know a thing about writing code and won’t understand any technical explanation as to why this can’t be done … just dreaming.)