Allow to override the toggle label

Thanks @rp7, I totally agree! Additionally, I'd vote to allow leaving the value entirely empty, like in views bulk operations.
As Drupal's regular checkboxes also have no label for the checkbox, I'd vote that to be the default. It would also save a lot of space in the forms.

I'll prepare a MR from your patch.

Here we go, I think this is more flexible and has better UX, otherwise you can never get rid of the label.

Added a small comment regarding the default value for the exiting sites.

Would be necessary an upgrade path for existing sites to make this change transparent for them?

While we are here, would be great to have a simple test for this new feature.