Ribis Because it's a totally impractical workflow. You shouldn't have to do a bunch of exporting & importing with extra files and 3rd party software just to modify one single tilemap. On top of that, you lose all reference to your other objects and tilemaps in the layout when you bring one over to Tiled for editing.
Imagine if you had to do this with Photoshop. Say you're working on something with 4 different layers but Photoshop doesn't support scaling so you have to select the layer, export it to a new file, open up a 3rd party tool, import the file, scale up the image with no reference to the other layers, export that file, go back to photoshop to import the file, then repeat for each layer. That would be completely unacceptable...yet for some reason people think it's fine here.
when I was using tiled for making one level with 5 layers with 5 different tilemap, I was making all of the map with tiled, and when I finished the map, I just export and import inside construct2... the workflow was faster than use construct2 for making map... I don't like to make map inside construct2... in my opinion is better to use a specific software to do the works... when I have to make an animation I use different software than construct2 (you can use construct for making animation, there is any problem) but with another software is better... anyway it depends how the game is...
(anyway is just an import, you can setup everything in tiled and after that you can import the map with the tilemap inside construct2)