How to specify a synonym for the table name in data properties when defining a general level?

I am defining a new general level and I want to use a synonym in the table name just like the t_ep_cto_parent has a synonym of t_ep_cto_parent as its table name but then references columns in t_ep_cto_child table.

When I try to do the same thing by defining a synonym for a table I cannot find the synonym in the list of values for the table selection in the level definition data properties form.

I have tried several things, always the columns for Key Field, Code Field are greyed out follow whatever is typed in the table name.