There is a limit of 99 tracks on a single timeline, but the audio and video on all tracks should be fully usable. I can do some experimenting and see what I can find, but I have two suggestions for you.

In the short term, the quickest way to make this work is to save a copy of your current project and remove all content from the top 15 tracks, then select the next 14 tracks' contents and drag it all up to the top tracks.

Place the the fully produced clip on Track 15, and then uncheck the video Enable/Disable this track box for the top 14 tracks. Produce to the same profile as your original clip, and hopefully the SVRT option will appear and PD will quickly add just the audio from the 14 new tracks to the produced video without changing the video content at all.

Do the same thing for the remaining 6 tracks, and swap out the original video on track 15 with the newly produced video, then produce using SVRT again.

If you're comfortable sharing the entire project, use Pack Project Materials under PD's File menu and save the whole thing to a cloud folder on OneDrive or Google Drive. Paste a shareable link here so others can download the project and see exactly what happens on their systems.

Quote There is a limit of 99 tracks on a single timeline, but the audio and video on all tracks should be fully usable. I can do some experimenting and see what I can find, but I have two suggestions for you.

In the short term, the quickest way to make this work is to save a copy of your current project and remove all content from the top 15 tracks, then select the next 14 tracks' contents and drag it all up to the top tracks.

Place the the fully produced clip on Track 15, and then uncheck the video Enable/Disable this track box for the top 14 tracks. Produce to the same profile as your original clip, and hopefully the SVRT option will appear and PD will quickly add just the audio from the 14 new tracks to the produced video without changing the video content at all.

Do the same thing for the remaining 6 tracks, and swap out the original video on track 15 with the newly produced video, then produce using SVRT again.

If you're comfortable sharing the entire project, use Pack Project Materials under PD's File menu and save the whole thing to a cloud folder on OneDrive or Google Drive. Paste a shareable link here so others can download the project and see exactly what happens on their systems.

Thank you so much for the help. I'll pack the project materials and start uploading them. It's 4.5GB so it might take awhile.
In the meantime I will start to work on the method you mentioned as well