https://www.xda-developers.com/pair-android-wear-without-factory-reset/
How to pair Android Wear (or Wear OS) watches to different phones without factory resetting your watch
I tried the instructions on the website at the link above and it actually works pretty well. It allows you to pair your Android Wear smartwatch with a different phone without a lot of hassle i.e. setting everything back up again. You have to be comfortable with using ADB on the computer and connecting to your watch via WiFi.
Before trying this method, I was reinstalling via ADB several Android apks along with setting up other things on the watch. This eliminates all that work and really helps if you switch between phones often or even every once in a while and want to continue using your same Android Wear watch. I do this with my Verizon Wear24 watch along with a Pixel XL and a Note 4 currently. Update: I do this with a Note 8 now and it works fine.
Read the instructions carefully. The short version is this (at the Windows command prompt or the Mac terminal window):
[code language="text" wraplines="false" collapse="false"]
C:\Users> adb connect 192.168.0.85
C:\Users> adb shell "pm clear com.google.android.gms && reboot"
C:\Users> adb connect 192.168.0.85
C:\Users> adb shell am start -a android.bluetooth.adapter.action.REQUEST_DISCOVERABLE
[/code]
And then connect to the watch using the android wear application. That's it!