Make MPO tweak a three-state control (#4897)

* refactor: make MPO tweak a three-state control

* docs: explain MPO tweak states

* docs: address code review comments

* refactor: make Multiplane Overlay config-driven

functions/private/Invoke-WinUtilCurrentSystem.ps1

@@ -61,7 +61,7 @@ Function Invoke-WinUtilCurrentSystem {
             $serviceKeys = $entry.service
             $entryType = $entry.Type
 
-            if ($registryKeys -or $serviceKeys) {
+            if (($registryKeys -or $serviceKeys) -and $entryType -ne "Combobox") {
                 $Values = @()
 
                 if ($entryType -eq "Toggle") {