I would have wanted to do a PR but Im not even sure what is the expected behaviour on mobile when you cant hover and a header link can have a URL how do you collapse/expand a header link section?
To avoid introducing a behavior change, I suggest hiding the arrow icon on mobile view to prevent users from thinking they can expand or collapse sections. The expanded state should be the only option since the functionality was never implemented.
On a side note, since you have setting to show/hide the arrow icon, you can’t dissociate a click on the header title and arrow.
Perhaps we could enable the expand/collapse functionality on mobile only when no URL is assigned and clearly document that both options cannot coexist. Additionally, I think having a URL in the header with a dropdown may confuse users, as it’s not immediately obvious that you can click on the title, so I would encourage the admin not to do that.
A very nice piece of work. There’s one uncertainty that may or may not be an issue: when clicking the dropdown arrow on the mobile end, the page automatically scrolls to the top.