maybe im not the only one but is it time for syncing from iPhone to iwatch and Mac when I delete messages in my phone it should delete in all platforms, or multiple messages to delete in Mac? deleting them one by one is a bit if time consuming.
New messages will arrive at all platforms. There is no syncing when you delete messages. At least I've never found a way to do this. I never really wanted to though because I haven't gone out of my way to delete messages since I had an old android phone that would slow down if I had too many messages.
Messages are synced across Macs, iPads, and iPhones if you turn on Messages in iCloud. Messages deleted on one device will get deleted off the others too.
The only exception is the Apple Watch. There is no syncing here. Messages deleted on the watch do not get deleted elsewhere, and vice versa. The watch only retains the last 30 days of messages it has received, so I don’t bother deleting messages here since they will eventually get deleted automatically anyway.