You can use an if-else condition where the button is clickable if the calendly link exists. If the link does not exist(else case), you can display a relevant notification
You can use this feature to see if you’re looking at the right row. As I stated, if you simply have an open link action, I believe the button won’t display if the row you’re connecting to doesn’t have a link.
It just shows that the column is linked to your button. The fact that it’s visible or not depends on if the row you’re connecting to on that screen has a link or not.