To fix backward-search synchronization (SyncTeX) between Skim and TextMate set Skim > Preferences > Sync > Preset to "Custom" with the command pointing to this script file and Arguments set to '%line "%file"' (without the single quotes). The problem is that (for as yet unknown reasons) the Shift-Cmd-click in Skim started opening a new editor win…

skim-mate-relay.scpt

#!/usr/bin/osascript

on run argv

    set mateScript to "mate -l " & item 1 of argv & " " & item 2 of argv

    tell application "Terminal"
        set thisTab to do script mateScript
        set visible of window 1 to false
        delay 0.5
        do script "exit" in thisTab
        delay 0.5
        close window 1
    end tell 
    
end run