A big problem for users coming to Silhouette 3 from version 2.3 is the lack of some shortcuts that made the roto workflow in 2.3 so fast and comfortable.
The number one shortcut that is missing is the good old "Shift+A" to toggle between Alpha Overlay (with motion blur) and the Foreground.
The problem is the new "Node" architecture where you can only see motion blur when you're looking at the Output Node.
But the guys at SilhouetteFX listened and have added all the necessary keybinds so the old 2.3 workflow is now possible again (Well done guys!).
The ingredients are actually in the default keybinds.py but you still have to modify it a bit.
Below is an updated rgba() function. Just replace the old one with this one.
# RGBA mode
rgba_mode = False
rgba_prev_view = 0
rgba_prev_view_node = None
rgba_mode = not rgba_mode
rgba_prev_view_node = fx.viewer.viewNode
rgba_prev_view = fx.viewer.viewMode
fx.viewer.setChannelMask(fx.Color(1, 1, 1, 1))
fx.viewer.setChannelMask(fx.Color(1, 1, 1, 0))
So with this function added you can now tweak your splines in the roto node while looking at the Roto Node Foreground View and by pressing "Shift+a" you can now jump to viewing the Output Node with Alpha Overlay and normal Overlay disabled. Pressing "Shift+a" again brings you back to the Roto Node Foreground View.
One very important shortcut that is still missing is a shortcut for looking at the Composite with motion blur. At the moment this is unfortunately not easily done.
SilhouetteFX would either have to add a keybind to enable/disable nodes (in this case the Composite Node / At the moment i don't know why there is a Composite Node anyway but maybe they want to add more sophisticated stuff to this node later) or add a Composite View to the Output Node (which would make a lot of sense imo).