GDevelop now has tilemap painter. See the release notes here Release 5.4.207 · 4ian/GDevelop · GitHub
I have a opinion to add a in-built tileset editor in the app. Some features that would help others a lot is - we can select a bunch of tiles from the tileset editor and we can edit their points like a sprite, and can save them. Again when we would need the properties we can press left shift or right shift to gain those properties again. When we save them another custom tab can be created and the saved tiles would show up there. And we can also edit the custom tiles like a sprite. There should be 3 tabs in the section where the objects a categorized- One for the tileset, one for sprites, text etc. and another for the custom tiles that we have saved(as told before). If you like my opinion, please add this feature as an update🙏 . Rate the opinion. I gave this opinion cuz I couldn’t make the player go behind object through the LDtk maps