It’s not the worst strategy (and is actually referred to as ‘peppering’ your password)… but if your primary use-case is websites and mobile apps, using a password manager like Bitwarden and randomly generated strong passwords is still a better strategy (and probably faster too, since you don’t need to type it out manually anymore, and/or remember which flex you used when creating your ‘peppered’ password).
This is a good approach if you have to login to services that aren’t via a web browser though - e.g. Remote desktops etc.