Default Data Graphic Style

When I select a column field to apply a data graphic to, then go to Data->Configure, the "Edit Item" data dialog box opens. I set "Displayed as:" to "Text" and "Style:" to "MyStyle". MyStyle was created as a Duplicate of "Text callout" Style, after which I changed its default fill color.

When I de-select that same column field (i.e. turn it off), then turn it back on again it defaults to the "Text callout" Style instead of "MyStyle".

How do I get the Text Callout Style to default to "MyStyle" instead of "Text Callout" so when I turn it off and on it always goes back to "MyStyle"???