I want to make my own folder of grouped objects where I store my assets. I then want to be able to drag and drop it into any blender file so i can use group instance to access that folder and import any model i want. I know there are simpler ways to do this, but i wanted an entire library similar to the extra objects plugin. The only problem is I cannot access the information inside the .blend file. If i could access those files without the need to open blender, i could transfer data between blender files easily. Is there a way to do this?
blender files use a custom binary format for a lot of stuff, so you really need to open blender to modify them safely.
There is a bit more information here: How would you go about reading a .blend file? I mean all of a .blend file, not just the .obj information
The best way to achieve similar functionality would be to do it as an addon within blender, so blender can handle file operations.
What you are describing sounds like appending an object from a Blender file.
Make a master blender file containing the objects you want (that you can bring in with a copy/paste) and then append (ShiftF1) specific instances onto a new blend file from there.