I make many games in gdevelop but face same problem many times my problem is i want delay of 3 or 4 sec when scene change
Perhaps you could start a timer when you get to the scene change
Condition: (whatever your trigger is to change scene.. maybe all enemies dead?).. Action: Reset the timer "nextscene"
Condition: Timer "nextscene" greater than 3 seconds / Action: Change scene
You can create a black box and chance the opacity to hide scene old and show scene new