The problem with complex passwords is they are hard to remember, and writing them down is obviously counterproductive. Password managers were developed to generate and store complex passwords for you so that you only need to remember a master password (which should still follow our previous recommendations).
While many companies offer such services, NGOs interested in Internet security for activists usually recommend the following:
Other online password managers exist, but their track record is not up to par with those listed above. Lastpass for example was breached in 2022 with devastating effect after numerous security specialists alerted them about vulnerabilities they did not fix correctly.
Firefox's integrated password management tool (formerly Lockwise) is an interesting option, but it requires adding a master password to be safe.
Are password managers safe?
Technically, if someone gets your master password or your password manager of choice gets hacked, all your accesses will be exposed. This makes them a single point of failure and an obvious target for hackers. On the other hand, if your primary e-mail password gets exposed, all your other accesses are also at the mercy of a simple "forgotten password" procedure, so you already have a kind of vulnerable master password.
Make your master password complex, but easy to type and to remember
You will be typing this password a lot. Your future self will thank you for keeping it simple, especially if you use it on devices that do not have a standard keyboard such as a phone or tablet.