Hi, I only recently started running this game but I found something on accident:

On Imperial Grand Prix there is this cannon right after the tunnel section that can be fired if the player presses the Activate Item button near it while not having an item.

I've found that this cannon will always open the shortcut if used, so if you don't blast it open yourself in the first lap, you can fire the cannon and it will be open in the second.

The important finding is that apparently either the cannon ball or the function to open the shortcut does not get reset if you reset the race while the cannon ball is still in the air. This means that in the next race the shortcut will already be open on the first lap, even though you never had to open it yourself that lap. On time trial this means you can skip the jet boost through the tunnel and its wonky physics and instead go straight for the warp boost, making for potentially much faster times.

I tested this in Time Trial mode on an unmodified copy of the game on a Windows 10 PC, I'll attach a video to show the glitch in action.

I don't know if this is a valid tactic for time trial runs, I don't think it's a lap skipping glitch but it might be against the rules regardless, the mods will have to decide that.