The following files are removed when an extension is removed:
PRODUCT_ROOT_D/admin/htdocs/modules/EXTENSION_ID/PRODUCT_ROOT_D/admin/plib/modules/EXTENSION_ID/PRODUCT_ROOT_D/var/modules/EXTENSION_ID/
Here, PRODUCT_ROOT_D is /usr/local/psa on Linux systems and
%plesk_dir% on Windows systems.
If an extension file cannot be removed, the removal procedure fails.
All files that are used by an extension should be removed by the
pre-uninstall script.