In the toolbar on the left of the screen, select the Split Conductor tool and click the conductor on the pole you want to split it on.
Once the conductor has been split and separated into two constructions, you are able to adjust the height of the separate constructions.
To do so select the pole with the Move and Select tool
Then find the Attach Points section from the Properties tab on the right and adjust attachment heights and change constructions as required.
To rejoin conductors, use the Join Conductor tool
Click both the conductors you want to join.
This will automatically merge them into one conductor.