I use the contextual menu in “v” mode to create guidelines. I also often find myself wanting to create a guideline while in “l” mode, but the contextual menu doesn’t show there. I think it would be nice to have the “create guideline” available in both modes. And I’d even suggest that guides created in “l” mode be set for “Measurement” automatically.
Maybe it would also be nice if, upon creating a guide with this contextual menu, the guideline was then selected.
I would also find it useful if a guideline remained selected after double-clicking the node to turn it perpendicular.