on our Montana 3400 we had the same board. I put a couple of hinges and a catch on it and turned it into a cabinet door so I could use the area behind it for storage.
You might want to double check your drain hose for your fridge. It should be sticking partially out of the outside fridge vent. The hoses have been known to become brittle and break causing the moisture to leak inside the coach instead of outside and could be one source for the mold you found. You can replace the hose with a section of clear plastic tubing from the hardware if your's is damaged.

Phil

We have a Montana 3455SA. We, too, put hinges and a handle on that board. I use it to store my baking pans such as cookie sheets, etc.