The standalone level editor I built and published in a repository has been updated with all the lately features I added to the tool:
New Ui design
Zoom in and out
Some geometry primitive such rectangles, lines and circles.
Tiles and backgrounds.
The only thing not working from the game is the ability to play the custom levels from the editor.
If you find the tool useful but don't want to download the game here you have the repository:
https://codeberg.org/glitchapp/Grid-Level-Editor
If anyone uses it to create any level for any other project I'll be happy to know, although it has been built for very specific rules, you can tweak it to fit any purpose which not only includes levels but also graphics (to do so modify the export library).
I hope you find it useful!