Thank you for tip!
Unfortunately, that didn't work: I've cancelled the game's folder, and erased the LiminalDreams one in the AppData subfolder, in order to do a clean install. I've made through all the worlds in order, discovering all secrets, and after I got the TRAVEL button I flipped the switches in the order shown in the video (green, purple, yellow, orange), but it didn't work: still, yellow and orange are the only squares lit up.
I'll add a screenshot of my progress:
If only there was a way to contact the developer about this...
The only big difference in my playthrough was that I pressed the switches as I was normally completing each level, I didn't wait for the red room to press them.
Except this which may be the reason, there was still ONE little detail, while playing in the exact order in the image:
I literally forgot about the scroll in the green world, and I didn't collect it, not even after getting 4 stars in the secret blue world.
You can apparently get in the blue world without the scrolls, though I still don't surely know if I have completed the game or not.
