Onion addresses rotate. A bookmark pointing straight at a single raw address goes stale when the market retires that address, and a retired address is exactly what a phishing operation sometimes picks up next.
Bookmark the canonical URL page on this site instead, or another reference you trust to keep a verified, signed list. When an address changes, the reference stays valid and you copy the current address from it. That way a rotation never strands you on a dead or hijacked address.
Store the bookmark inside Tor Browser only, not in a normal browser that syncs to a cloud account.