How to copy/paste a value of memory window

You can use the Debug command Display (D) which prints the results in the Command window.

You can select the lines in the Command window and copy to Clipboard (right mouse click or Ctrl+C).

http://www.keil.com/support/man/docs/uv4/uv4_cm_log.htm

You can also save sections of memory to a hex file:

http://www.keil.com/support/man/docs/uv4/uv4_cm_save.htm

You can do formatted output in Debug Functions:

http://www.keil.com/support/man/docs/uv4/uv4_printf.htm