Have you tried this?

http://kyticka.webzdarma.cz/3d/moi/#CLineCommand

Hi Mark, yeah the command Stargazer shows above is the closest thing to that.

re:
> Maybe hold down a key (without a tool selected), then click and drag to draw a guideline.

The thing that's tricky about this is that when you have no tool selected you're in selection mode and things like "built in" modifier keys (like just Ctrl click without any other keystroke) are focused on selection related things then rather than drawing type things.

- Michael

Spirit of the Guide Helper Lines is to work with only the Function called! ;)

Call any function
Click without relase, move, release

---can be make before the first click of the function, after the first click of the function, before the last click of the function---

Don't forget that you can press 1 second on the little "white mark" for have more functions of the Helper Line itself
(Right or Left click)

Move - Re Orient - Rotate - Division Snap - Projection Next Point

Of course you can use the plugin for persistant Guide Lines but no need with some training! ;)

No problem. I will carry on with things as they are. It was just a thought. I do already use the K and Ctrl K shortcuts to keep and delete construction/guide lines when needed.

Thanks

M