Thank you so much for your response.
In the following illustration, here are the controls I speak of:

In my plug-in, they are not there. It is blank.
I ‘just’ thought of something. Maybe they are not there because the particular footage I am using is not requiring an alpha channel (i.e., the plug-in is actually not required here). If the footage did, indeed, have enough black background, the controls would appear(?)
Again, your thoughts.
Al