A Polyline Tool like AutoCAD has would be very helpful. Going from a line to a curve with a short cut would speed things up.
The Weld Tool will take a series of lines and turn them into a Polyline.
Fredo’s Bezier Spline Toolset can create and convert lines into many different types of linework.
Keyboard shortcuts can be created for SketchUp tools/features … including installed plugins.
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