I think I found a bug. When setting a default for the GlyphView and UpdateCurrentGlyphView, it won't be visible until I reopen the GlyphView.
For now all I want is to set the grid. Maybe it can be done more simple? Here is my code.

from lib.tools.defaults import getDefault, setDefault
from mojo.UI import UpdateCurrentGlyphView

print getDefault('glyphViewGridx')
print getDefault('glyphViewGridy')

setDefault('glyphViewGridx', 32)
setDefault('glyphViewGridy', 32)

UpdateCurrentGlyphView()

Thanks, Thom

UpdateCurrentGlyphView() just refreshes the glyph view, it ask to redraw. It will not update defaults / preferences

You can update the defaults in all views by posting an preferences changed notification.

from lib.tools.notifications import PostNotification
PostNotification("doodle.preferencesChanged")

similar to the ShapeTool see https://github.com/typemytype/RoboFontExtensions/blob/master/pixelTool/PixelTool.roboFontExt/lib/PixelTool.py#L109

good luck

Thanks again Frederik!