Open/Save dialogs on my Mac (macOS 10.14.1) delay about 0.5 to 1 seconds.
How do I change this delay to zero seconds?
You can change the speed of the Save/Open dialogs with Terminal. Enter this into Terminal to change the speed to the default:
defaults write NSGlobalDomain NSWindowResizeTime 0.2
Change the number at the end to speed up or slow down the animation. The following is practically instant:
defaults write NSGlobalDomain NSWindowResizeTime 0.001
This is not specific to the open/save dialog however, it reduces the time of all animations on the system that read this value.