L for light WSDA to navigate on tile textures, X Rotate tile, Ctrl picks a tile, G toggles grid, shift+clic to edit colision layer (pink is path and not colider)
To save, I did it a lot coz its buggy and I needed to refresh page several times (it worked better on chrome). Clic on save icon, rigth clic on image and save it(its your map!) Then you can load it by clicking on top left corner and send your file.
There is no icons for some props like water drops, enemyes key stuff.
I didn't get how to put messages.
If player go on border map its freezes. Careful to leak. Save before cliquing on enlarge screen or click on it when start to make map coz sometimes the game re-sizes strange and canot save/edit or recover it, need to refresh and lose your data.