Get mouse click in Game View or save data in runtime

Hello to all.
I would need to draw lines in the Game View window but in edit mode.
At the moment I can perform this operation in runtime mode inside Update ().
But I have some difficulties.
Normally I create meshes in my custom editor by drawing them on a plane and saving the vertices in a list. Everything works fine.
Now I’m trying to get the same thing but drawing in the Game View window and as mentioned there are problems. I can only use Update () and then with the application started.
Is there a way to get click on the plane visible in Game View but in edit mode?
If this is not really possible how should I do to save the list of vertices created in runtime that is lost when the application is closed? I verified that all meshes created in runtime are lost along with the data in the vertex list.
Can you please give me some indication? Alone I can not find a solution.

Can you suggest me how to save a Vector3 list on disk to be able to access it later?