Very happy to see that Dorico 4 has eliminated two former problems with renaming Expression Maps.
Renaming a map used to create a new map with the new name, listing it at the bottom, while retaining the old map and name, which had to be deleted. Now it works as expected, renaming the same map with no new map created.
Renaming a map used to have no effect on the End Point. Instruments assigned to the previously named map were retained, so a reassignment to the new name was required. Now it works as expected, with the Endpoint assignments automatically reflecting the new name.