OK. The current entry states:
Parameters can be provided by adding a “dictionary” of key / value pairs to the block but can also be left empty if not necessary. The dictionary block can be found openhab blockly “lists” section where you can find more information on how to use it.
It’s that second sentence which seems important in this case, and at the time I didn’t understand that this was a MUST. I will edit the wording a little to try to make it a little clearer.