Sharing your own entire screen, or just one application window, is very easy. Just click on the "screenshare" participant control, and choose from the popup what you want to share. I decided to share the LibreOffice Writer window where I'm writing this chapter. Also, I changed the conference layout to "overlaps", and now conference participants are little picture-in-picture live videos superimposed to the live video from my application window (which can be a slide show, a spreadsheet, a terminal, whatever).