I’m using the EzySlice framework to cut meshes (GitHub - DavidArayan/ezy-slice: An open source mesh slicer framework for Unity3D Game Engine. Written in C#. · GitHub).
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So far it can cut a mesh but infinitely but I want to be able to cut partially like this:
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As you see in the 3rd photo, only 1 vertex is created at the end of the dotted line away from the outer edge. However the rest of the vertices created by the cut are in pairs. How do I achieve this effect?

As I understand it, you want something similar to the Knife tool from Blender. But I’m afraid creating such a tool in Unity is very difficult, and perhaps not possible.