Beginning on a custom pixel engine brush and attempting to create a new default smudge brush preset - the standard smudge options do not add themselves to the list of settings.
For example, the pixel brush engine shows the following settings:
☐ Size
☐ Ratio
☐ Spacing
...
☐ Scatter
Then when I click the plus button to add a new smudge brush - this list stays the same, without displaying the options to adjust smudge length, smudge radius, and color rate.