I create artificial tabs all the time. I've done this in the PAC Project Demo (http://www.opto22.com/site/downloads/dl_drilldown.aspx?aid=3172) and our EMU energy monitoring HMI (http://www.opto22.com/site/pr_details.aspx?cid=4&item=OPTOEMU-HMI).
Create a window to hold your tab buttons. Then create the overlapping windows to hold the content displayed for each tab. I prefer to remove the borders and resizing features of the content windows using the menu option Windows -> Properties for each. IF you remove these features, you may have to manually enter the window's x, y, height, and width coordinates to get the tab window to align flush with the content windows. Once you get one content window's properties, you can use them for the other content windows. Do this as a last step, which is after you've edited the content within your screens. (Once you remove the dragging and resizing handles, you have to use the menu to switch between windows in Configurator, which can get tiresome if you are doing a lot of work between windows, copying and pasting and such. However, your tabs will make it easy to switch between windows in Runtime.)
Assign operator driven attributes that show and hide all windows so that when you click your first tab, all windows with content for the tab are displayed, and any others are hidden.
Here is an example from my SNAP PAC Demo:
My tabs are graphics, but they can be simple buttons or drop-down menu items. My tabs display the factory, ship, Learning Center, Pump, and HVAC screens. All of these tabs are in one window that stays visible. Just below the tab window are the various content windows for each tab. Each tab button uses the windows operator-driven attribute. I've shown how to reach this feature and how I am opening and closing windows to achieve the desired tabbing effect. The screen for the Ship uses even more windows, which you might want to look at. Both of the HMI samples I linked to are free.