I am running a 100 amp service from this panel to my new building 200 feet away, will be using 2/2/2/4 aluminum buried wire. my question is this, am I okay to just use the open space on the upper left of the panel for my 100 amp breaker? The bottom left breaker is to an outside generator outlet with the required lockout for the main when in use, I have never used this since I have lived in this house, and although it would make installation much simpler to do away with that, as soon as I did I would probably need it and regret it, I could relocate all of the rest of the breakers on the left up a couple of spaces to make room for the new breaker, but is this really necessary ? Thanks for you help

This is the best photo I can get of this limit switch, I don't have the switch so cannot attempt to take a closer-up photo for perhaps more clarity. Hoping somebody might recognize the brand/manufacturer and also especially as well be able to read or have a clue what it says in that line of information as can almost be made out just below the lighter colored bar toward the upper section.