I haven't tried this, but I suspect that you should be able to save as PDF and then convert the PDF to jpg.
I tried that already. Despite I set orientation to landscape, it exports as portrait. And therefore it cuts some parts off the layout, because dimmensions are not the same.
Selecting a landscape orientation in printer/page setup and then choosing save as PDF should save the PDF in landscape orientation, but even that is unlikely to match the dimensions of your monitor screen. That would require adding a custom paper size that does match your screen dimensions to your default printer driver and then selecting that page size just before saving as PDF.
Your other option may be finding a screen capture utility that allows you to omit the portions of the capture that you don't want. Don't know of one off hand, but suspect a google search might turn something up.