I changed my twitter handle recently. How can I change this on my Stack Exchange profile?
Your network profile is updated from your oldest Stack Exchange account, so you'll have to edit that account to see the changes reflected. It can take a while to copy the changes across.
The Twitter URL in your network profile is part of your About Me section; the newer Twitter ID field added to user profiles is not yet supported by the network profile; presumably that will be rectified once all Stack Exchange sites support the new profile options.