Split Screen Dodge & Burn

[Big_Stan 15]

I am doing Dodge & Burn with 50% gray scale mask.  Carl Surry did an excellent tutorial fro this process based on translating a PS tutorial.  Other achieving the 50% gray scale, the PS tutorial is fine and Carl did a very good job showing how to get the gray scale with AP.  

In the PS tutorial, the author showed a split screen; the gray scale mask (he called this a "visualization layer") next to the Pixel image.  How can I get the same side by side view in AP?

[Lee D 426]

Only when using certain filters do you get an option to change the view to split or mirror views so you get a before/after preview.

[Big_Stan 15]

Thank you.  Will  you please point me to a tutorial that discusses the "certain filters".