I'm somewhat puzzled as to why you would require two screens.
Firstly, it's entirely feasible to have two separate Webex sessions
operating on a single computer, provided they originate from distinct
hosts. Assuming the student holds a student Webex account (which is often
included in the Webex chat app), or if you possess an additional host
account from another instructor, you can indeed run both sessions
simultaneously. BTW, this capability isn't mirrored by other web
conferencing platforms outside of Webex.
Secondly, why not opt to screen-share while utilizing a collaborative
whiteboard tool like Google Docs? This approach allows for collective
participation. Remarkably effective solutions such as Mural and Miro
whiteboards could also be employed. There's a possibility of integrating
these solutions more deeply within the Webex framework, but even if that's
not the case, a simple screen-sharing strategy coupled with the
distribution of a whiteboard link through the chat function can yield
productive collaborative results.