Extend concat to support array concatenation...
An example use case would be to the concatenation of two parameter arrays, like ui-locations & service-locations. Concatenating these parameters would enable "copy"ing over the concatenated list of locations. You could stand up Microsoft.Web/serverFarms based on this concatenated list. This might, however depend on the creation of a new "distinct" function, so that you can iterate of a distinct list of locations.
Gijs Walraven commented
This is already possible.
"value": "[concat(parameters('firstArray'), parameters('secondArray'))]"
Paul Daly commented
Here's another example use case: