Thank you for your message.
Unfortunately, multiple monitors support is not implemented in the Viewer for Mac/Linux yet. However, we plan to add it in the subsequent updates. Sorry for the inconvenience.
In addition, please note that we have moved your question to another topic related to Viewer for Mac/Linux. In this topic, you can also find a full list of features currently available in Viewer for Mac/Linux, as well as the features that we plan to implement in our future updates - please see the very first message in the topic here
Hope that helps.