It would be nice if I could attach a document with drag and drop when working with the attachment control, instad of pick a document up.
Mostly the same way as it works in the document library.
I need the drag and drop feature and the ability to paste from clipboard
I need the ability to choose more than one attachment at a time.
In addition to the idea mentioned by OP:
Today i've noticed that it's possible to drag and drop documents towards an attachments-control if the control's datasource is a SharePoint list. However, this doesn't seem to work when the datasource is a field on a CDS entity.
Upvoting this idea; it'd be really nice to see this implemented! From a business point of view, drag & drop is something the end-user expects by default. It's quote annoying that we're forced to select 1 attachment at a time.