While the whole comment thing is great, it’d be nice to be able to throw a nice large post-it note in our Blueprints. We could put ToDo lists, Bugs we’re working on, misc. notes we want to remember, or comments for other developers. I honestly can’t believe this isn’t already in the engine. It’s such a simple thing and would make many of our lives easier to be able to create a “note” that isn’t necessarily attached to any specific piece of code like a comment is.
You can create comments without any node inside it…
I use it a lot for BP commentary:
Sticky note on you’re monitor? 
Better than getting arrested for display homicide. (Got caught once during a screenshot) 
As KVogler said, comment nodes do not need to be attached to any specific thing and can be used for exactly that.
You can press C while the mouse is over an empty space in the graph to create a new comment (or right click and use Add Comment…). Pressing C while nodes are selected wraps them in a comment as well.
You can edit the color or use whatever search tags you want. For example, if you start your comments with “TODO:”, you can use Ctrl+F to find all references to TODO in the Blueprint or use Ctrl+Shift+F to search all Blueprints in your game in order to make a TODO list.
Cheers,
Michael Noland
What could be improved a bit though is the text could be there in a bit smaller font, so more text fit in less space.
If that would be a multi line input field, it would be awesome.
It may not be inutuitive to everyone that you have to use Alt+Enter to create multi line text for the comments…
Huh… live and learn. 
As of 4.7 (I think, it certainly is in 4.8) it is a multi-line text block, you can use Shift+Enter to add additional lines. This is the same convention used for all other Slate multi-line controls.
Adjustable font size seems like a good idea, entered a feature request (UE-16085).
Cheers,
Michael Noland
You can create comments without any node inside it…
I use it a lot for BP commentary:
[/QUOTE]
Yes, and that is what I am currently doing, but it’s nowhere as clean as a nice well done note system. As
you pointed out, it’s almost there - just take it the rest of the way. The current system is fine for small
notes, but I typically have small novels in my code with large TODO lists and using the existing comment
block is far from ideal…
thats why u should have a design document
I/we have something in the works which might help you with this:
We are not quite ready to announce but expect to hear something soon 
I would suggest picking up Word of Level Design’s Preproducion Blueprint eBook and if you want to go one step further than I would suggest either Blake Snyder’s Save The Cat books & software and/or Nevigo’s articy:draft 2
There is also a great thread which goes further into these tools here: Project Management Integration with UE4 - Feedback & Requests - Epic Developer Community Forums
If none of these tools are of interest to you I would suggest just sticking with either Word, NotePad or Sticky Notes
On the topic of sticky notes,
I would suggest taking a look at these: https://teslaamazing.com/
I’ll let you know how well they work when mine get delivered sometime within the next month, personally my plans are to use them as a agile board + general design notes, etc for large world map planning.