Smudge option in paint grayed out

Operating system: MacOS High Sierra 10.13.5
Slicer version: 4.8.1
Expected behavior: Smudge option available when using Paint
Actual behavior: Smudge option always grayed out

I imported brain segmentation for editing. I can paint and edit but cannot access the smudge option. Any suggestions? Thanks.

Smudge option is only available in recent nightly versions of Slicer.