Motion Effects on customized pixel sub-sections

[Brad Stucky]

Is there any way to apply motion effects on a customized sub-section of pixels?  I noticed that you can add effect rows for sub-sections like nested pixel stars, or create rectangles on a matrix, etc, but after I have copied a 150x16 matrix prop to another grid view, enabled channel level for the prop, re-arranged and converted selected pixels to 36 specific grid view groups, I noticed the right click menu doesn't have the option to Add/Modify Motion effect rows for these grid view groups. Is there some other way to do this?