i observed that when deleting all comps except folders, my file saved at 3.5 MB. i rebuilt the identical folder structure from scratch; the saved file was only 11 KB – 0.3%!! 99.7% of the larger file is garbage data.

I built a user template from old projects, deleting the data. It was slow to load. I deleted all the comps and kept the folders because sometimes I only need the folders. That file was the 3.5M file. I looked inside the aepx but could not delete the data (not sure what to delete). I built the folder template from scratch. 11kb

I suspect the data may be from RotoBrush or a similar plugin. Most likely the source project had a Rotobrush effect that was deleted to make my folder template, but the data was not cleared.

I cannot upload the aep files or a zip file at this link.