'Typical Scales' List in all versions - how to add/change

Corel comes with a preset list of Scales.  There is one spot to create a custom scale.  I use Corel to do permit drawings about 40% of the time, and 1" = 10', 1" = 20', 1" = 100', ... are VERY common permit site plan scales.  Corel does not have them in the list of defaults.  Is there a way to customize the drop down 'Typical Scales' list?