How to reduce tooltip appearance delay in Xcode?
Tooltip delays can be adjusted globally from the command line. To reduce it to one millisecond (1/1000 second), fire up Terminal and enter:

defaults write -g NSInitialToolTipDelay -int 1


To only affect Xcode, tell the defaults command to only alter that value in the Xcode preferences domain, rather than setting it globally:

defaults write com.apple.dt.Xcode NSInitialToolTipDelay -int 1


I believe if you're running version 5 (?) or earlier of Xcode, the domain used to just be com.apple.Xcode , so:

defaults write com.apple.Xcode NSInitialToolTipDelay -int 1


If I am missing some other prefs domain they've used, this command will show the top contenders:

defaults domains | tr -s ', ' '\n' | grep -i 'xcode'


To reset anything you've changed, just run the same command above you used to shorten it, but change the 1 on the end to the "factory default" setting of 1000 (1000 milliseconds = 1 second), e.g.

defaults write com.apple.dt.Xcode NSInitialToolTipDelay -int 1000