“a midi file that grows to over 60 gig”…that sounds weird. Can you pls elaborate on this? Where is this midi file? You will certainly not succeed to use VST Transit with such files.
“laggy interface” - where, when? We like to help, but this is just vague.
“unable to hide tracks” - fixed next version which is in the making
“no way to use freezed vst instruments” - will check.