I'm asking the same.
I tried to do some setting, save them (S key) and then Reset (R key) , and then load setting again(L key) and it works well but only while oculusmirrors is launched.
If I try to load setting using command line parameter --LoadSettings, it complains about missing previously saved settings file. (what I have no idea how to store. S key seems to not save setting into a file)