I have a query regarding library part configuration properties, using SW 2022, SP 4.0

I have created a library part of an angle profile which has various configurations. I used a design table to do this.

I right click on a configuration 'Properties' to show the configuration properties. Selecting 'Custom Properties' makes visible the 'Properties' window.

On the 'Configuration Properties' tab I have included a property name titled 'Description'. I assumed this would dynamically update with data from the design table. The dropdown box in the 'Value / Text Expression' field doesn't list the expression 'Description'. 

Can someone explain how I can add a Description in this field, so I don't need to manually add it?

Thanks.