Your “Watched” status should not be tied to a specific PMS / Library. If I look at shared content or other Plex servers that I own it should know my Watched status. Not having this is very frustrating right now especially since I move content between servers regularly (home and colocated server).

Have you tried doing this with the trakt plugin?

Sync "Watched" status

Topic		Replies	Views
[Feature Request] Watch Status Sync Feature Suggestions	1	147	April 8, 2018
True 'Watch Status' between PMS Servers Feature Suggestions granting-access	1	109	December 22, 2021
Watch status across servers (with same plex account) Feature Suggestions	35	596	September 8, 2022
Syncing of watch status between multiple Plex Servers Feature Suggestions	5	260	July 22, 2016
Store Watched/Unwatched on User Account Instead of Server Feature Suggestions	4	206	April 7, 2019