Thanks for posting in the Community space, yogi4.
In QuickBooks Online (QBO), able to set up a customer credit limit alert is not an option.
I know how the feature you want would be helpful in the program. The Community recognizes feedback and suggestions from customers like you which can help us improve our product and services to our customers' delight.
While we continue to make your experience with us even better, I recommend visiting our QuickBooks Blog to get the recent news, information about the latest features, and updates in QuickBooks Online (QBO).
In case you have any other QuickBooks concerns in the future, visit our Community help articles for a guide.
Please know that I'm always here to help you if you any other questions about QuickBooks, leave a comment below. Have a nice day.