Align 2 faces with only two vertices and constraints I want those 2 faces to be on the same plane only by moving A on the C axis and B on X/Y/Z. I tried to resize with transform orientation to normale but I cannot lock the other vertice position. Maybe a tool displaying the normal numerical values of the two face would help. The rest of the mesh is currently hidden.
Is there a tool or technique to do that ?
I'm confused with the question so here are a few options.
To flatten the faces on the $Z$ axis, for example, select all vertices, scale them to zero (press  S + Z+0)
You can modify the coordinates for any point numerically. Enter edit mode (↹ Tab) enable the Sidebar (press N) to access the Item Properties panel.
You can see the Local and Global coordinates and manipulate them at will.

So you can flatten the faces first and then, with all vertices still selected, you can set them at the correct coordinates numerically.

To move a vertex along an existing edge, use Vertex Slide (⇧ Shift+ V)