How to avoid unselect file dialog when pressing minus sign in Midnight commander on macOS
You need to edit ~/.config/mc/ini config file and look for only_leading_plus_minus entry. By default it is set to false which causes this behavior. If you set it to true

only_leading_plus_minus=true


then - will trigger Unselect dialog only if - is the first character you type which pretty much would never be a problem. If you do not have only_leading_plus_minus just add it. Make sure you do not have Auto save setup enabled in your config and if you do, quit all instances of mc prior editing your ini.