I create a .sgu file in BIAB 2019 v614 and save to disk.
Take a close look at the mixer from BIAB for this file and look at the two MST tracks in the first picture

Then I open Reaper, insert the BIAB VSTi and load the same .sgu file I had just saved. Take a close look at the VSTi loaded in Reaper in the second picture. Now note that the two MST tracks which I had inserted in BIAB have now returned to the original tracks which I replaced when I loaded the MSTs. Also the two midi tracks have turned into Audio.

Can this be fixed in next patch?

Save it in BB as a new Style SPIDERS2.STY then save the song and load that in the vst.
I have that style in my list but I can't load it and can't save it as it says it's not in C:\bb|Styles
otherwise add those in as extra tracks with Select > Select a Super MIDI Track...

You can't change the existing tracks in a style as the vst looks for FullPathStyleName=C:\bb\Styles\SPIDERS.STY

look at the BBInput.txt in the saved tracks folder as it is generating make a copy of it before it deletes it.

I found SPIDERS it was in a bonus PAK installer, I have the Audiophile drive but it wasn't on that.
I saved it to a new style SPIDERS2.STY, save the SGU, did a slow Rebuild in the VST's Style picker, open the SGU in the VST:

Pipeline, thanks for the special attention. I appreciate your effort on this issue. I see this as a partial workaround since I generally have no need to "redefine" a style once I customize my song. I hope PGM makes this a bit less convoluted. But, in the meantime I will give it a try.

But what about the fact that the midi super tracks are not midi in the VSTi. Those two MST are audio only? Certainly that has to be fixed?

And one more very minor almost nitpicking suggestion if PGM is listening... Can we harmonize on colors - Green audio, Yellow midi, Blue MST?

Otherwise, loving the progress with V614 and the VSTi.

Sideline on your topic. You said you are running BIAB 2019 v614?

I only see the upgrade patch for 613 on the support page.

???

This has been floating around on the black market...

...do you not have access to the pre-release forum? 614 is still on the pre-release forum, but here is a link to the installer:

Download build 614 update patch

V614 shows a lot of BIAB VSTi love.

OK I gave it a try.

After about an hour this was a total bust! I could not find a workflow that could reproduce what you are showing. I am not saying it can't be done, just saying I can't do it... in an hour.

My workflow is simple - Carve out the chord chart and initial instruments in BIAB then move all midi and RTs to Reaper for recording and mixing.
Bottom line: the .sgu file in BIAB needs to be able to just be opened in the VSTi and show the same instruments.

I am going back on the road for the week for the day job, but will return next Friday night. Sure am hoping this bug will be fixed when I return.

Still messed up over a week later. Take a look at this morning work:

Pic on left is BIAB 2019 32b and on Righ is VST3i 1.11.11. This is the exact same .mgu file opened in both windows. Noticed the difference content on the tracks. I think we have seen this before when the VSTi is using a version of a style with instruments which may have been changed in the song.

This apparent pre-requiste to have a style where an instrument has been changed saved as an individual new style in the directory is really burdensome.