I often have a piece of paper and often scribble some bits on it to assist with logic..sometimes its easier to see something laid out in simple drawings rather than think it in your noodle!
If this is too big an ask, how about a tab that lets you add relative notes. For example, when typing code have a control+other key which puts a date stamp and allows the user to make some notes. Yes we can all add this to our code in remarks but sometimes this gets ugly. The relative bit would mean that when this is added a marker is put in the source file. When on the source file marker the relative notes pop up....hey presto bobs your uncle and fanny is your aunt (sorry very english saying!).
any thoughts?
