How to Create New File in Selected Folder Using LaunchBar?
This can be done by using the "New Text Document Here" action

Select folder -> tab -> start typing "New" -> select "New Text Document Here" -> type name -> enter.

If you're looking for a more complete solution that can create any type of file (including ones without the .txt extension that the New Text Document action forces) try this Applescript. Just put it in a file named New File.applescript in the ~/Library/Application Support/LaunchBar/Actions/ directory:

on handle_string(dir)
    display dialog "Enter filename:" default answer ""
    set fname to text returned of result
    set fullpath to dir &amp; fname
    try
        do shell script "touch '" &amp; fullpath &amp; "'"
        open location "x-launchbar:select?file=" &amp; fullpath
    on error errMsg
        display dialog "Error: " &amp; errMsg
        open location "x-launchbar:hide"
    end try
end handle_string


It'll touch the file, then select it in LaunchBar upon completion (you can comment out the line that does that by adding -- to the beginning of the line or just removing it).