Keynote: How to skip "open presentation" window?
This is determined by the ‘NSShowAppCentricOpenPanelInsteadOfUntitledFile’ key. Setting this preference to false will show the new document view by default.

defaults write com.apple.iWork.Keynote NSShowAppCentricOpenPanelInsteadOfUntitledFile -bool false


If you would like a new document to open with a set theme instead of with the theme chooser, go to Keynote Preferences and set For New Documents: Use theme.