Deactivating tasks manually is much more complicated than simply removing them. It is not enough just to change a registry entry from "1" to "0". schtasks tool applies various values to the registry that cannot be easily replicated. But removing is pretty easy, just remove some files or folders and some registry entries that are easy to track by task ID just Ctrl+F the ID in TaskCache key.
Files and folders are located in C:\Windows\System32\Tasks
Files and folders are located in C:\Windows\System32\Tasks