as mentioned in the Plex-Wiki (Click me - Section "Setting Agent Preferences (Currently Mac OS only)") the possibility to set agent preferences is currently only available for Mac OS users or by manually editing the configuration files - which is a real pain.
I thought the new Web Client would adress this limitation but as i recently discovered this sadly isn´t the case.
Is there a plan to solve this issue?
Yes, we plan to address that in the new web client. The new web client is definitely still a work in progress. The most recent update added the ability to reorder agents in the advanced preferences, modifying agent preferences will eventually be added as well.