Can I remove the "delete all sessions of the session manager" checkbox?

Hi there Mozilla Firefox team,

can I remove the "delete all sessions of the session manager" checkbox?
I use the extension "Session Manager" ("Sitzungs-Manager") and I accidentally checked the stupid checkbox above mentioned, which is present in the Tools \ "Delete private data" dialogue out of whatever reason?

Can I somehow "hack" the about:config or another part of Firefox to remove this line or is there no way around just backing the file up regularly?

Thanks for your help in advance!

Kind regards.