Thank you DerOmega for your fast respond.
However, I'm afraid I cant find that function, at least not on the A7 version of MED.

I did go to Edit -> Manage Frames -> Add New Frame
If I make the source frame the first frame of my animation, my character will have the same pose as the first frame, but that wont solve the problem since changing any frame before my new frame will still move the bones in my new frame.

For example, if I have 3 frames. I finish the second frame and start working on the third one, and then decide to change something in the second frame. The bone in the third frame will also move relative to the second one, and I have to redo frame 3. If I have multiple frames, that is a big problem.

If someone knows how to fix this, please let me know.
Thank you.

Salim