The profile folder was Electron's default from the product name
("Theseus Navigator") and add-ons lived in addons\ under it. Now:
%APPDATA%\Theseus\extensions\ installed extensions
%APPDATA%\Theseus\extensions-data\ per-extension storage + scratch
%APPDATA%\Theseus\extensions-backups\ replaced copies
%APPDATA%\Theseus\extensions-staged\ staged updates
Both moves are one-time migrations on the first start that finds the old
layout: the profile folder is renamed (same volume, instant) or copied
when a rename is refused, with the old folder left in place in that case;
the four sub-folders are renamed before the extension host first reads
them. Nothing is deleted. THESEUS_USER_DATA still overrides everything.
The host now hands each extension its data folder as api.dataDir; the
Screenshot and PDF editor add-ons used to rebuild the old path from their
own folder for scratch files (so they recreated addons-data\ after the
move) and now use the field, with versions bumped so the bundles reseed.
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