This article about Sophos Switch stacking is great.
https://support.sophos.com/support/s/article/KBA-000009707?language=en_US
However it doesn't tell us HOW to make this happen, nor does it link to such an article. From what I hear switch stacking is still on the roadmap. Maybe there is one way that is in use now and a different way coming?
If there is a way to do this now, a link to the how-to article would be great.
You don't have a Sophos Switch or a Sophos Central Category so I just chose Sophos XG Firewall. That's another idea. Update your product documentation feedback to include all Sophos products or have an OTHER option.