Web browser: Mozilla Firefox, recent version.

Steps to reproduce:
1. Go to Personalization->Models.
2. Edit "Top clicked" model.
3. Click "Segments" section.
4. Start adding new segments group.

Actual result:
The "Available segments" toolbar on the right is not floating.

Expected result:
The "Available segments" toolbar on the right floats and it's visible when scrolling the page down.