I've made a lot of progress in this today

Now there can be different pages of objects

I've added more objects

Look at the thing that took me 3 hours to do (just the object selection systems, now it is made through arrays, it has animations and fixed a bug the previous prototype had)

That's how the editor looks so far, I will try to spend all day today adding objects, working in more keyboard shortcuts, implement pages and also, add a trigger editor

I did a little progress on the level settings

Just fixed a problem with the fonts, it looks much better now, right?

Now the background and ground colours can be changed

Just started working in the level settings in the editor, with what I've got so far, now the song of a level can be changed

Some Geometry Dash: Legends screenshots I took.