One trick in ERG can be to slow your cadence 5-10 rpm before the stomp section (maybe 10-30 seconds early). It increases the resistance because of the lower rpm, and give you more “bite” at the beginning.
This will vary from trainer to trainer because of resistance levels and flywheel inertia.
You can sure swap to Resistance mode. Easy on Mac and PC, but a pain on mobile.
I’m not sure if this is what you’re asking for, but my trick for exceeding a workout’s wattage during a sprint (on a Tacx Neo) is to start out in a low (large) gear in back and shift to the next higher (smaller) gear every few seconds. This way I can keep ahead of the reductions in resistance that the trainer makes. Of course this only works for short sprints like 30 seconds or less; otherwise, you run out of gears.