change standard app for unknown file type

I wasn't able to change the standard app for opening a filetype, that is not in the list in bridge settings. My .blend files are associated with an earlier version of blender. I can do right click -> open with every time, but it doesn't save the change.

the list in the settings doesn't allow me to add .blend as a file type to change the standard app.

Did I miss something or is this a huge limitation?