Add vertice?

Let`s say i have two not connected aligned edges that i want to connect. They are different long. For that i would need to add a vertice at the longer one of the edges by hand, move it to target location, and then weld the two vertices. That`s at least how my workflow looks in trueSpace.

Is there a way to add a vertice at a edge?

I do not fully understand what you are attempting(is it on same object/mesh?), but for adding a vertex to an edge:-

You could use [sub_object edge] Geometry > Break (will break an edge into equal number of parts)
Or
Use [sub_object vertex] Visual tools > Create/insert (with edge snapping on)
Or
Use the streamline tool [sub_object vertex)] "D" (similar to create/insert, with need for edge snapping enabled)

could also just useing the steamline cut tool, with one edge selected and tapping it to spilt the edge in 2.

I had forgotten that one, probably because I removed that functionality from that tool. (I would sometimes have an edge_loop selected, run the streamline cut tool to add an edge/cut, but then later find the edge_loop I had selected at the time was now with added vertex. Took me a while to realize what had happened lol.)

Create/insert (with edge snapping on) , or Cut without snapping was what i was searching for. Thank you both

Sorry for my weak description. The shot should make it clearer what i want to achieve. That the smaller part is just half as high as the bigger part is just coincidence. It may be in any ratio to each other.

It`s about level design. I use several equal parts to create my level, which i export as one piece and clean it up to have one single mesh then to save draw calls. I need to close edges. Closed in terms that there shouldn`t be gaps between the parts. Not fully closed like a cube. When i leave gaps then i have not only higher vertice count, which is bad for performance, but also sometimes the problem that you can see through. So i try to close the geometry where ever possible.