This issue have been fixed with hub 7.80, which reads User Tag from robot.cfg and put them into hub.cfg automatically during hub probe upgrade.
With Hub v7.80, when user tags are added/modified to robot.cfg this change will propagate to the hub.cfg automatically after a hub restart.
For this mechanism to work the following key must be enabled (value = 1) via Hub Raw Configure:os_user_retrieve_from_robot = 1
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Note: This only works if the hub.cfg does not have any user tag already. The robot.cfg overwrites the hub.cfg existing user_tags only if the above key is enabled and if only if the user tags on the hub.cfg are empty.
The user tags set in the hub.cfg (via Admin Console) instead will overwrite the robot.cfg user tags.
This is documented on docops article below:
Changes to User Tags for Robot Alarms Sent by the Hub:https://docops.ca.com/display/UIMPGA/v7.8+Hub+AC+Configuration#v7.8HubACConfiguration-MigrateUserTagsfromtheRobottotheHub