Maybe I used a wrong word, but “sandboxed” was the word I read many times in discussion about the location of the “support” folder which contains all the themes, plugins, addons …
In RW5 it was easily found in the user’s Preferences folder, in RW6 is hidden in a different directory.
I could not remember where it was, then I found this topic:
Reminder please where Stacks Folder is located in RW 6
~ / Library / Containers / com.realmacsoftware.rapidweaver6 / Date / Library / Application Support / RapidWeaver
I restored the situation of two days ago copying that folder com.realmacsoftware.rapidweaver6 from the Time Machine Backup.
I did not move single files but all the folder taken from the backup.