Using a sheet of paper right now, am in the process of switching to a self-written password manager. It uses Vigenere encryption using a key that is not saved anywhere (that I have to remember) and saves to a .dat file. Should I use my own tool or a service?
It's admirable that you have the knowledge and skill to build your own password manager, but to me that seems like (re)building the Queen Mary when this year's brand-new Jet Ski will do everything you need it to do. As you're most definitely the technical type, you really should check out Bitwarden.