Button/modifier key to quickly unselect all but one engines

[linusg]

A common use case is seeing what the results of one specific engine are, which currently requires manually unselecting all other engines. There should either be a button to unselect all, or something like Alt+click unselecting all but the clicked checkbox.

[CanadaHonk]

You can unselect all easier now with groups and the heading checkboxes, but I like the idea of alt+click too.

[linusg]

Current solution seems fine :)