1. Run a command prompt as administrator.
2. Navigate to where the psexec executable is located.
3. Run .\psexec -s -i cmd.exe to open a new cmd window.
4. In the new cmd window run taskschd.msc (or %windir%\system32\taskschd.msc).
5. Edit your task like before. You shouldn’t be prompted for credentials.

Source: windows 10 – Can’t modify task “Reboot” in win10 home – Super User