I am going through this document and this is what I gathered.
<Esc> Escape key
<C-G> CTRL-G
<Up> cursor up key
<C-LeftMouse> Control- left mouse click
<S-F11> Shifted function key 11
<M-a> Meta- a ('a' with bit 8 set)
<M-A> Meta- A ('A' with bit 8 set)
<t_kd> "kd" termcap entry (cursor down key)
However I don't see how I can map Command/Apple key here. I am using plugin mentioned here. It works great. I open a tab and then I hit Command-R and I get the list of files. I could not find where the mapping is done between Command-R and the function. I am using vim settings as mentioned here
The modifier "D" stands for the "Command" key. See also :map-cmd-key in the official Vim documentation.