Adding a new switch into the middle of an existing stack

roriol,

I believe your goal is possible.  Kindly read below: 

1. Since you have an existing stack numbered 1-2-3-4, remove Switch 4 from the stack for the meantime.  Kindly access the article below as reference guide:

How do I remove a switch from a stack on my managed switch?

2. Connect the new switch as Switch 4.  You might want to preconfigure it before joining the new switch to the stack.  Kindly read pages 492-493 of the M5300 Series Software Administration Manual here about Preconfigure a New Switch Before Joining the Stack.  

Also, refer to this article below since it seems that you will be adding a new switch at the bottom of the stack: 

How do I add switches to an operating stack on my managed switch? 

Or, refer to this article below since it seems that you will replace switch 4 with a new switch: 

How do I replace a stack member on my managed switch?

3. Reconfigure the old Switch 4 as Switch 5.  Renumber switch 4 as switch 5 (you might need to configure everything from scratch).  Kindly read pages 494-495 of the M5300 Series Software Administration Manual here about Renumber Stack Members.  

Note:  If ever you are not confident to try the steps above on your own, feel free to open a chat/online case with NETGEAR Support at anytime for assistance. 

Regards,

DaneA

NETGEAR Community Team