The normal-mode command to move to the end of the line is $.
You can copy to the end of the line with y$ and paste with p.
To copy/paste between different instances, you can use the system clipboard by selecting the * register, so the commands become "*y$ for copying and "*p for pasting.
$ move-to-linebreak
$
y$ yank-to-linebreak
y,$
"*y$ select clipboard-register yank-to-linebreak
",*,y,$
"*p select clipboard-register paste
",*,p
Check :h registers for more information.