it used to be possible (2018) to select a line or any drawing object on a chart, then press shift to copy at any time as you drag the object with the mouse... it just worked and enabled fast chart annotation.
Now it only seems to work if you are meticulous in the order of key presses:
select object, drag to new area on chart, press shift, release mouse button, release shift key.
Can you test this please to see if it works as intended, user experience is definitely worse for me.