As @Kronbits said, most of these suggestions are under development and the others are on our roadmap.
About the point 5 though, I personally use this tool for my games, which I make with GMS2 and It's actually pretty easy to import, as the spritesheet is ready to do this :). This are the steps I follow:
1. Export the render effect from the tool, in the name suggestion you will have something like _100x100px which indicates the size of each frame. (The number of frames will also be added to the suggested title in the future.).
2. Import the spritesheet to your GMS2 project.
3. Open the sprite in the image editor and go to. Image > Convert to Frames.
4. Add 100x100 (or whatever your number is) to Frame Width/Height. Set "Number of Frames" and "Frames per Row" to a very high number, like 999. Accept.
5. Go to Image > Auto Trim All Frames.
6. Delete extra frames (this are caused by the spritesheet, having the exact number of frames in the suggested title will avoid this step.)
... and done. You have your animation trimmed and loaded. It's really easy and straight forward once you do it a couple of times.