Since this is optional, it should be moved to a method

This makes sense, especially as this will help not making breaking change to the API. Just to confirm, are you happy with having two functions, like:

• toggler(label, is_checked, closure): Toggler (existing)
• toggler(label, is_checked): Toggler

And add a method (and maybe a *_maybe variation):

• Toggler::on_change(impl Fn(bool) -> Message + 'a)

Is that what you had in mind?

It's fine to make breaking changes where necessary. There should be a method if we make the message optional. But we may want to wait for the iced rebase before we do this.

I see so better hold off and go ahead with the current state? Or would you still want to see the Toggler::on_change method in that PR?

I think we should wait for iced to be rebased before making new changes to iced

Make sense. Would you suggest blocking this PR and dependencies then? Appreciate there currently seems to be a blocker on iced rebase, so perhaps this change could go in as is, since it included minimal requirement for toggle matching an acceptable UX for async operation.
Alternatively, thinking about the Bluetooth screen, I could put something like the text("...") with the toggler is not available.

Appreciate all options are sub-optimal here, but just keen to get the ball rolling for COSMIC :)