Don’t. You’ve got two functions - send a pulse to do something, and report a steady state.
openHAB doesn’t natively support pulsey toggle stuff, so we have to simulate the action. To get the pulse out on Modbus, we have to command an Item on and off. Meantime, we want to command an Item ON to turn stuff on, and expect to stay on.
So two Items.
One Item represents the light state, we use that on the UI (or rule) to send ON and OFF commands. Link that to the Modbus state reporting register.
The other Item represents the pulse. Not interested in this for the UI at all. We set up a rule that listens for commands to the steady-state Item, and - only if required - sends a ‘go’ pulse to the pulsey Item and so onwards to the Modbus action register. Followed shortly by a ‘stop’ pulse.
