As soon as you load the tweetdeck page an event listener gets bound to the entire page which checks if the action menu for a tweet is open. As soon as an action menu is opened the link to that tweet is put onto your clipboard for sharing. No need to press the "copy link to tweet" button ever again.
Button to press to get the link is shown in the red square here:
Whenever it is pressed the script waits 2 seconds and then once again initiates the event listener to check for a new instance for the action menu to open for when you want to copy another link at a later time
Personally I have not noticed any slow down, however my system has high quality hardware so I cannot say how this will affect low-to-medium specced systems.