Hi.
I've made a small, simple program to insert my own files for the kneeboard in to the mission file. The program adds the folders "KNEEBOARD" and "IMAGES" to the .miz file, and selected files to the "IMAGES" folder, "jpg,png,jpeg,pdf" PDF files is converted to .png. I have only tested the program on my own computer, so I don't know if it works for you. No special program, just one I made to add my own files more easily.
Added some language if you wanna try it.
If you want to try it here is the link:
https://drive.google.com/file/d/1OFHx25dHd1C3z6XJzULrLLxBhGVNk17L/view?usp=drive_link