I don't know of any macros to do this, but you could turn on the notes/balloons selection filter (F5 to toggle filters menu) then do a blanket select of your whole sheet and turn off leaders/arrows in the properties menu. This filter will also select text annotations so may not save time depending on your drawing. A Quick CTRL+Click on the notes to deselect them will quickly leave you with balloons only.
There might be an advanced filter setup that only grabs balloons and not notes but my menu is currently locked out so I can't check for you.
It's a shame you can't set a "No Leader" option in Document Properties. This would be a very quick way to do it.
Thank you very much Oli. this will work for now. i agree that this should be an option in the document properties.
There isn't an option in Document Properties for Balloons to not have a leader, but you can create one Balloon without the leader, then copy and paste as many as needed.