How do I turn off the "Flow Switch" while posting something on iMac?

Or did you meant Follow switch?

If you don't want to receive emails when people reply to your post tap the blue Subscribe bell so it goes white.

Or go to your forum preferences and turn off specific notifications

It does not matter which device you use to post in ASC.

Alan Blair wrote:

How do I turn off the flow switch when I post something?

What Flow Switch ?

Once you press Post, there maybe a momentary refresh of the web page while it uploads your posting