The below registry hack will allow you to Open applications with multiple windows / tabs with single click. Single clicking will open the last active tab, while hovering mouse over the program icon will show all open tabs – like before.
Go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
Go to Edit->New->DWORD (32-bit) Value
Name the value LastActiveClick
Hit enter to assign the value and change it to 1
Restart Explorer and you’re good to go