Problem setting up custom profile for G 25 wheel

I am trying to set up a custom profile so that I can modify the default G 25 settings which, it seems, cannot be modified and saved unless one does so. However, so far as I can see, the G 25 does not have enough assignable keys to enable one to fill in all the fields, which is necessary to save the profile. However people seem to be using the G 25 in a modified form so I’m wondering how one gets around this problem. I would be grateful for any suggestions.