I made a minor change to add keyboard commands to the Linkage program. It already supported the typical Control-C, Control-S, etc., keyboard shortcuts for operations like Copy and Save. It now support single key operations like C or J for Connect and Join, as well as a few others. They are all listed in the documentation.
The Windows installer file can be downloaded and run to install Linkage 2.5.8.
After I posted this originally, I added some new simulation controls to pause and step forward and backward. Stepping is in 1/30 second increments as are all steps of the simulation in any mode.