Hi Vladimir,

re:
> Is there any way to automate this kind of rounding of two-dimensional geometry?

Try the attached InsertCircle script, it will insert a circle into your 2D shape with every click which places the circle's center point.

Instructions for installing a plug-in here.

It works like this:


Hope that helps! - Michael

EDIT: 5/29/2021 - added "Flip" option.