Do you mean the height of the bottom menu area? It's in Preferences, in the Monitors panel. There's a "Menu Height" text box.
Another thing you can do to quickly make the bottom area go larger quickly is press Shift-~ (tilde) and the menu area expands temporarily to almost fill the screen. Good for when you're working on the timeline and you quickly need to see large graphs without permanently adjusting the menu height in prefs.
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Greg Niles
combustion Product Specialist
Discreet