The [Client name] is found in the table I’m using this view for. On the other hand, I can put expression on DISPLAY NAME of an app created views like the below:
In certain situations, there are roundabout ways to accomplish this. For example, if a view is based on a slice that comprises only a single row, then you can use an expression that references that row from the slice even though it’s not possible to reference the current row from the view.
The restriction shown in the yellow box is not due to the fact that it’s a manually created view, it is because it’s a collection view (shows multiple records).