First of all, want to share my appreciation that you haven't abandoned VP yet.
Installed 6.0.0 (6573) on an M1 macbook under Big Sur 11.6. It opens documents.
I haven't dug too deeply as I don't want to endanger existing docs with corruption if something goes wrong, so only working with copies. Well, to be honest I did open some docs in VP6 that are shared on Dropbox and they don't seem to be corrupted in VP5.
Only thing I noticed on a quick run through is that you've removed the Pages Drawer. Is that going to be deprecated? Would hate to see it go, as I do use the Drawer as a handy navigation aid. The only alternative to see all the pages in a document is to use the floating Pages menu, but that's just not nearly the same. Most of my documents have an Index page with the drawer permanently open and then I open and close other tabs as needed.
After over a decade of using Voodoopad, I never knew that I could access line spacing from the Format Bar. Learn something new every day. I'm amazed.