Using AttachPoint, you can create "attach points" on the frames of your sprites. You can then export the code and use it in your game to attach an object to another.
When you export, it asks you the name of the state/sprite, which is used for the array's name. The attach points for that state/sprite are also saved to disk, so you can later load them by using the "Load Points" button and entering the name.
The code exported is made with GML in mind, which is used in GameMaker Studio 2, but it can be used in other languages as well if they support array literals.
What kinds of sprite sheets does it support?
At this point, it only supports horizontal sprite sheets for animation. Loading multiple sprites will treat them as separate sprites, not an animation.
Does it support GameMaker: Studio 1.4?
No. Currently it only supports GMS2, because versions prior to GMS2 do not support array literals.
Samuel Venable for those DLLs. Thank you!