I think this is already answered but I’ll add my two cents anyway.
As I’ve said in other posts, Items are the coin of the realm. Rules mostly work on Items. Persistence exclusively works with Items. Sitemaps and HABPanel exclusively work with Items.
I’ve never been a big fan of the triggering Channel events because it breaks this nice clean division between Items and Things. It sets up expectations that you can do more with Things. But the purpose of them is to avoid the awkward approach that was used previously of a Switch that gets momentarily set to ON and immediately set back to OFF. Since all you care about is the event, the devs set up these triggers so you can trigger the Rule on the event straight from the Channel rather than requiring an Item. But the assumption is that this event is ephemeral. There would be no reason one would want to keep this data around in an Item or the like. So from this perspective it makes no sense to be able to assign this type of Channel to an Item.
Are you referring to PaperUI’s Control section? Because you can only add Items to the sitemap as far as I’m aware.