I have just migrated my first project over to RW6 and can’t wait to get started. It looks great! All my plugins, stacks and the theme for this project (HV-Rainbow) are up to date but I’ve lost all my custom theme styles as created in RW5. The only post I found was this one RapidWeaver 6.3.1 Beta 2 but it is now closed.
I manually copied all the custom styles in the “Theme Styles” folder on my old mac into a new folder I created in ~/Library/Application Support/RapidWeaver/ . This did not work. I’m sure there must be a fool proof way to retain all the custom styles - this is especially important for more complex projects with multiple styles on different pages.