“New tab” button shortcuts:

Permissions used:

Access your data for all websites: to use containers.
Read and modify bookmarks: to detect when a tab has been dropped outside the sidebar (but not on the bookmark bar).
Read and modify browser settings: to use Firefox preferences and theme.
Access recently closed tabs: to reopen closed tabs.
Access browser tabs: to get URL, title and favicons of tabs.
Access browser activity during navigation: to trigger an extra animation when a page has finished loading its resources.