Comment 2 for bug 1847798

This is already possible, see the doc:
http://docs.kicad-pcb.org/master/en/eeschema/eeschema.html

"The symbol reference is #+5V. The reference text is not important except the first character which must be # to indicate that the symbol is a power symbol. By convention, every symbol in which the reference field starts with a # will not appear in the symbol list or in the netlist and the reference is declared as invisible."