Thank you ! I did find it around line 70.
In French the default word for "log out" is "déconnexion" which is 11 letters and takes 1/3rd of the screen on mobile
Have a good day.
I could find the constant for translating/changing the connect button text in your language files(MOD_SCLOGIN_LOGIN) but I could not find it for changing the text of the log out button.