This issue was reported by @domenic here, and is being moved to the OpenUI repo.

This was a nice bonus I discovered upon reflection, and comparing with the old popup proposal.

If a developer wants some sort of custom behavior, e.g., "close all other toasts that are of a similar application-specific type", or "no force-close but yes light dismiss", then they can accomplish it using popup=async plus some custom JavaScript code for the entertoplayer handler.

This is good! It counters any arguments that, by providing somewhat-opinionated classes of UI, we're doing something too magic that will make developers sad.

I think this is worth pointing out in https://github.com/mfreed7/popup#classes-of-ui---dismiss-behavior-and-interactions .

(Also it may feed into the bikeshed discussion, e.g. popup=manual might be a better name than popup=async.)