I’ve started to code a drawing app in Javascript for a project (in which I use Shapr3D a lot) and made my line drawing tool a mix between straight lines and arcs. Using it myself, I find it quite fast compared to switching tools and performing multiple operations. See video clips for examples.
- Switching between line and arc is done with TAB.
- Arcs are defined by an initial tangent and then the endpoint.
Often when working in Shapr3D, I already know that I want a rectangle with rounded corners, but often I will draw a rectangle, 4 circles and then do a bit of trimming. With this concept, I can do lots of variations in a single operation.
There are of course downsides as well. For instance, if you don’t know the initial tangent this tool is quite annoying. But more often than not, the tangent is often 0° or 90° and this is faster.
I just wanted to share the idea. Looking forward to history based modeling! 
Ha ha you’re right, I’ve probably never really mastered the auto-setting… But once you get the hang of it, it works quite well. But, this isn’t available on Mac OS as far as I can see. I’ve been using Mac more lately, probably why I forgot about iPad…