For something as specific as this you would need a custom editor. The biggest problem with Tiled Map Editor if you’re scripting, is that it’s object properties in the editor only accepts one line (a string), and if you’re using a scripting language, there is also no syntax highlighting. Good luck writing scripts using only one line.
Also, in order to attach an image to an object, unlike Graal, you can’t just insert an image, it has to be a part of a tileset, which means you would have to either make each individual image a tileset (which gets messy with a ridiculous number of tabs) or copy the image of every single NPC you’re ever going to make (which obviously makes no sense for Graal) into a single image and use that as a tileset. Otherwise you can’t actually see the object / NPC you’re making while using the editor.
It’s sometimes great for general games if the developer is the one developing content, but it’s not good for something unique like Graal which uses user-generated content. You need a level editor custom-tailored to your game, especially if there is scripting involved. Otherwise it’s going to be a bunch of general-use stuff that doesn’t help at all.