Cannot Choose "Action"

Problem/Motivation

Cannot set the "Action" option as it's disabled/hidden via CSS.

Steps to reproduce

Create a menu with the mega-menu module installed and observe that the Action button is not displayed when editing a menu.

Proposed resolution

Don't hide this control.

Remaining tasks

Evaluate if unhiding this control is the right choice, or if this is a user error/misunderstanding.

---

Patch attached to implement the proposed fix.