Someone made a constraint based sketcher for Blender: https://github.com/hlorus/geometry_sketcher so that is fun..

But of course using a mesh modeling engine for CAD is not the best idea. You generally do want to work in B-rep, if not for precision then for exchange reasons (e.g. export electronic component models as STEP to add to PCB software, import a whole board STEP model from PCB software to build a case for the board)