I think there are a couple of solutions:
1) http
/www.office-forums.com/threads/one-to-many-connector.49635/
or
2)
http/visguy.com/vgforum/index.php?topic=6953.0
If you google "Visio many to one 2013" or some similar words and order you will find quite a number of links.
Hopefully one of them will be applicable to the overall requirements of your network map.
Is it a network printer? If so, you really do not need to have a connection from every computer to the printer per se. Just place the printer on the network and identify it as a network printer. Then it can be understood that all computers on the network have or could have access to that printer.
Simplifies the drawing....
You can likewise google "network diagrams" and see other examples that you may be able to emulate in some manner.