@Marcus Tang you can't watch cards, lists or boards on behalf people members, but you can:
1) Add them to cards which will mean they are watching the cards and will get notified
2) Configure Butler to send notifications to all board members when particular things happen
3) Mention them by username in a comment
Hello Community! My name is Brittany Joiner and I am a Trello enthusiast and Atlassian Community Leader. I'll be sharing with you a series of videos with my top tips on how to best use Trello...
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