From any search, just click “All criteria” in the bottom navigation bar, then click “Add all to list”.
All the users will be added to the list! This feature is very useful if you want to clone a list from your competitor on Twitter, for example. You just have to add a list as a source, then click “Add all to list”. You can also add a text file as a source, then add all to a list that already exists or create a new one.
Remember that Twitter allows 20 lists per user with 500 users in each list.