[trilinearnz]

In terms of storing your credentials, is your current Excel file password-protected? If not, I would do this at a minimum if you are committed to the Excel approach, and it's very quick to apply.

Alternatively you might be interested in other client-side options such as KeePass, which are more secure and provide a simple GUI (although arguably not as immediately-navigable as a spreadsheet). This could provide a more comfortable stepping stone if you're not wanting to commit to one of the more mainstream cloud-based password managers. Full disclosure: There was a security vulnerability in KeePass a few years back, so it's worth keeping this in mind.