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	2	145	February 24, 2022
True 'Watch Status' between PMS Servers Feature Suggestions granting-access	2	108	December 22, 2021
Watch status across servers (with same plex account) Feature Suggestions	36	591	October 27, 2022
Syncing of watch status between multiple Plex Servers Feature Suggestions	7	257	June 10, 2021
Store Watched/Unwatched on User Account Instead of Server Feature Suggestions	5	205	August 22, 2021