Cannot add a new empty group to a Matinee on Mac

In 4.18, it is no longer possible to add a new empty group to a Matinee on Mac. Instead of asking for a name for the new empty group, the Matinee editor now just displays a small white dot in the Track graph. This behavior does not occur on Windows.

REGRESSION:
Yes. This behavior does not occur in 4.17.2

1. Create a new project.
2. Add a Matinee Actor to the level.
3. Right-click in the Tracks tab and select "Add New Empty Group."

RESULT:
The right-click menu disappears and a small white dot appears in the track graph (see attached image).

EXPECTED:
The right-click menu disappears and the user is asked to provide a name for the new empty group.