How to cut out Polygon Boundary by two point?

I need to cut out Polygon Boundary by two point, such as this picture(red line is Polygon Boundary and blue line is new boundary), Can you give me some case?
Thanks in advance for you help!

Are you trying to select a part of a polygon by clicking on it at some points?

Or to delete a (selected) part of a polygon?

I just want to split polygon boundary by two point.can you give me some case?

Hello @n1ka - can you please give us some details about your setup?

We are happy to help, we just need more clarification on the issue.



Do you want something like this but with polygon?

Thanks.It is my fault :sob:.
1.My polygon is 2D or 3D-plane(but don’t have height).
2.A polygon, and then select two points on the boundary to form a multi line segment (support curves and polylines, the curve is composed of many polylines).