Should be fixed now. I've replaced the $util.navigate() call with a click_link() equivalent for non-links: $dom.trigger(element, 'click'). Couldn't test it unfortunately as I wasn't able to find out how to make the attachments UI show up, in a reasonable amount of time. Can you test it or give pointers?

https://github.com/ocproducts/composr/commit/bfa00849a0ea31ceddeca96d39ab1ce5b3977aea

Ah, it shows up with simplified attachments UI disabled, tested working now!