Displaying Multiple Cell Registers Simultaneously

How to display multiple cell registers simultaneously in Ansys Fluent?

To show multiple cell registers simultaneously, first define them that they exist as an object in the outline view. Apply all settings (e.g. color, filled, ...). They are stored with each individual object.

To display them, start with the first register (right click > display). Then open from the ribbon View > Graphics > Compose... and activate 'Overlays'.
Finally, display all other cell registers and deactivate the overlays option afterwards.

Note:

(a) Showing many cells with cell registers can freeze the user interface.
(b) Bring up the desired view before showing the cell registers to minimize interaction with the graphics window.
(c) Open all required panels before displaying cell registers to avoid redraw delays when moving panels around.
(d) Don't forget to disable overlays when you're done. It should be disabled when displaying the first element that you want to use for your composition and enabled for everything else.
(e) If you combine cell registers with contour plots, vector plots, pathlines or mesh display, keep in mind that the legends might not show correctly. Compose everything that is possible with a scene before using the overlays option.

For more details, refer to this document.