Cubase Pro 9.5.20
When importing MIDI files with HALion Sonic SE multi-timbral option, unknown tracks are created that can not be deleted.
File -> Preferences - MIDI - MIDI file - Import Options
select “HALion Sonic SE multi-timbral” from Destination pull down
(see 1st attached)
Import any .mid file (new project or existing project)
several tracks are added, depending on the .mid file
Delete all tracks. Two tracks remain which can not be deleted.
One has a speaker icon which is not a track type for this version.
The other has no Track icon
(see 2nd attached