I'm impressed by your dedication to perfecting the model, even with all the twists and turns along the way. It's clear you've put in loads of effort to make it run smoothly, from tinkering with the loops to figuring out the right speed for those trains.
Using the LEGO Boost sensor to activate the coaster is a brilliant touch. It adds a whole new level of interaction and engagement, especially for curious visitors eager to give it a go. But you can check out the us theme parks as an example.
Expanding with more trains in the "knot" sounds like a thrilling challenge. Maybe you could experiment with different track layouts or introduce a clever timing system to keep everything running smoothly.