I created a new metric "Ext Price" which is SELECT SUM(Price * Quantity) from the "Order Line Items" table. When I go to put it in a folder, the only place it will let me put it is the "Orders" folder, which is the parent table of the Order Line Items table. Both facts involved in the Ext Price metric are from Order Line Items, and that is where the metric logically belongs. Why won't it let me put it there?

Metric folders work a bit differently. If the folder is not showing in the list, you will have to create it under the Manage tab, you will then be able to select it from the list:

Thank you!