Compartmentation combined with good encryption is the bedrock of any good op-sec. Who centralizes every secret in one location and brings it on their person? My most treasured intellectual property is stored in a Veracrypt container inside a flash drive protected with LUKS as a secondary measure. I keep it at home, and only open it on a secure OS (With no malware) preferably not connected to the Internet. I also have duplicated this in as many places as possible in-case one copy gets corrupted, and have memorized the password and don't have it written down anywhere.