Hi,

I need two small movies over third, big. Like here



I added 3rd on one layer, 2nd above composite and... what next? When I try to add next on above layer, it is added to 2nd not 3rd.

In the properties of the composite transition, you can select the target track. The default is "Auto" which is the next track down, so on your topmost track you want to select the track that contains the big movie.