Implode - tracks from midifike

I am importing a huge orchestral midi file from Cubase
The cubase file has different tracks for articulations (violin 1 arco, violin 1 pizz, violin 1 spicatto etc etc.)
If I implode these tracks, muscore puts them into separate layers. When I laboriously change them all to layer 1 I get unwanted rests. It will take weeks to remove the rests individually.
There must be a better way. (The file I’m working on is an entire symphony)

Since downloading , I’ve done all my writing in muscore - it is brilliant, (actually, an answer to decades of wishful prayer)

Thank you to all the people who have contributed.