icloudsafaritabs
Prior to updating to Safari 13, iCloud Tabs was a feature that, when turned on and on clicking the tabs button on "Desktop" Safari, would show you tabs that were open on other devices at the bottom of the list.
Here’s how they used to work per Apple's support documentation: https://support.apple.com/en-us/HT202530
I no longer see this list of tabs.
As of this writing, I am running Safari 13.0.1 on 10.14.6.
You can use this block of AppleScript to loop through your tabs on a window:
tell application "Safari"
repeat
repeat with i from (count of tabs of window 1) to 1 by -1
set thisTab to tab i of window 1
set current tab of window 1 to thisTab
delay 1
end repeat
end repeat
end tell
This will go through all your tabs and switch every 1 second. Just change the delay to change the time before each tab switches.
Glims for Safari is your friend.
After installation go to Safari > Preferences > Glims > Tabs Misc. and check "Set minimum tab labels size to favicon size".
You'll get something like this…
Best Answer
A Reddit user claims Apple support said they won't sync until your Mac is running Catalina.