I found this interesting because unbeknownst to me, I went to Find My in my 14 Pro Max (iOS 16.2) and I can't find that option for anything I own (Watch Series 8 (wOS 9), iPad 7th Gen, iPad 9th Gen (iPadOS 16.1.1).
I've went through several different Apple self help pages. The instructions that I've read are all pretty clear, except that I'm not seeing the "Left Behind" slider.
My phone screen looks exactly like yours.
I just looked at Find My on my iPad (9th) and I have the option showing up for my phone but not my watch.
I've marked your question as "Me Too" and I'll follow the thread.
I'm as up to date as I can be on the watch and phone.