Viewing multiple panels in IntelliJ IDEA sidebar

How much control do I have over the number of panels that are visible at once in the sidebar? I've gone over the docs and fiddled with the options but can't seem to figure out how to get what I want. I know I can do some "split view thing," but I'd like to know if I can view more than two panels at once in the left sidebar.

Moreover, in a panel with multiple "tabs," can I view two of these at once (eg. Project and Test panels?)