When I take notes in an editor or Googledocs or Evernote or whatever I use at the time I sometimes have information I really want to jot down in the contents of the notation.  An example would be name of a server and then usr/pwd at the same or next line.
Having 1 secret thing in a document makes the whole document equally secret.  That is a shame when the rest of the document can be read by colleagues and customers.

A solution can be to encrypt just the sensitive stuff.  In an editor it could be prefixed with <encrypted> or <encrypted login=”uniquename”> like so:

Just copy everything between, or including, the tags to an application and enter the password that corresponds with your name.  If you have an intelligent enough editor you can have a macro for the same; position yourself in the tag and choose Decrypt from a menu.

This way you can have a document with secret data without being afraid of it getting into the wrong hands.

One could also replace the encrypted data with a URI to an online storage or application for your secret data.  Working within the Microsoft stack one could have ones domain usr as name/login and let it work without having to enter any password.

One can have the same concept within a (text) field in a database.  Instead of encrypting the whole field and missing out on all the index capatibilities just encrypt the secret stuff.  This could also simplify some user management.

I see some difficult design choices when I mentally try to adapt the idea to a team and a person and a team of teams and some roles.  What makes it difficult is more of user/passphrase handling and not of implementation crypto wise.

Emacs has something like this with its org-crypt.el.
Evernote has it built in.  The encrypted text is replace with a small icon.  Open it and enter you password.  Simple enough.