How to triangulate a single face the way you want in trueSpace 3.2.

In trueSpace 3.2, there's no tool to add a single edge between two vertexes. Here is a method I came up with some years ago.

To keep things simple, we'll create then triangulate a four-sided, nonflat face.


Step one, click the Cube primitive button to create a cube, then click the Vertex select button. Click on one upper vertex of the cube, then hold Control and click the vertex diagonally opposite the first one.
Change the coordinate system to World (Wld) where the arrow is pointing. Hold the Right mouse button and drag the selected vertexes up a ways.


Step two, select the face then use the Bevel button and drag a bit to raise it enough where you'll be able to select the corner edges.


Step three, use the Edge select button to pick one edge, then hold Shift and click an edge which shares a vertex with the first edge. Now click the Erase Vertices button.
trueSpace 3.2 uses Control+click to select edges and faces that are not touching each other and Shift+click to select edges and faces that are touching each other.


Step four, use the Edge select and Erase Vertices buttons to remove the edge the arrow is pointing to.


Step 5, same as in Step four, remove the circled edge.


There's the new edge, exactly where you wanted it.