When you have a dropdown with multi=True, a user might want to select multiple items at the same time. However, dcc.Dropdown closes when you select one item, and to select another item you have to open it again.

It would be much more user-friendly if dcc.Dropdown can stay open when an item is selected, or at least have it as an option. With rshiny this is already possible, see the multi-select example here.

There seems to be a way to hack the javascript code to get it working, but a proper solution would be to have a boolean option in dcc.Dropdown, e.g. close_on_select, or multi_close_on_select.