I’m not sure if I understand correctly, but you can pass custom data for each vertex of your mesh through the uv/uv2/uv3/… attribute.
When using the uv block in the node editor, you can change the attribute:
You can pass vec2 values this way.
You can also use any custom attribute but at the expense of a little more work. See Using shaders exported from Node Material Editor - #5 by Evgeni_Popov