Retrieve Function App Settings:
$rg = "SOME_RG"
$svc = "SOME_SERVICE_NAME"
az functionapp config appsettings list -g $rg -n $svc --setting-names
az functionapp config appsettings delete -g $rg -n $svc --setting-names AzureWebJobsDashboard
Get a list of Function Keys:
$rg = "SOME_RG"
$func_name = "SOME_FUNCTION"
$a = az functionapp list -o json
$Func_list= $a | convertfrom-json | % { $_.name }
az functionapp keys list -g $rg -n $func_name -o json | convertfrom-json