Hello,

You can show your video if you select "Video" in the window which is in the right bottom corner and click on "play".

 But as you say, on the track you have only the thumbnail of the first frame and last frame, depending on the scale. If you want to see the frame detail, you need a video editing program like Magix Video De Luxe. MMM is more music  oriented.

A trick could be to cut your sequence in several parts with the keyboard short cut "T" in order to define significant key points to synchronize your music. The first frame of each part is displayed at each beginning of the segment, providing an help.

Regards