Square bracket characters are missing when opening notification body of a user task in business-central designer

Issue

I'm trying to setup a mail notification for a user task following this solution article What is the correct configuration for Notifications/Escalation of Human Tasks?.

But when I edit the Body content of a notification in user task, using the example code from Example A.8. Body of notification with variables in this document page, the square brackets [ ] are not loaded correctly in the business-central designer after I re-open it.