First configure the software as guided by member @limpu.cool here (Ultimate Night Usage Manager.).
then create a batch file, say Reboot.bat file with contents
Code:
"C:\Program Files\BroadBand\BroadBand.exe" /reboot
(Make sure, "Imran's Broadband Helper Utility" is already running when above command is issued.)
then schedule this batch file from your Jdownloader.
(I have tried this method with USDownloader, shall try with Jdownloader also after a few days)
Note: the software must be configured properly before you try this.