The line with the export command applies only to your current shell instance. As soon as you open another shell, it will not have this variable set. Even if you add it to your .bashrc or .zshrc, this will only be valid for commands executed in a shell.
You linked an article that explains how to make the setting persistent with LaunchAgents. Did you try this?
No, I didn’t try yet. I was wondering if this is what everybody is doing, especially given that it is not what the Bitwarden website suggests. Is that the best way to set the environment variable permanently?