<CustomTag>.displayFormat

[Gdg]

Hi,
I have a custom tag "BoxSet" and I'll like to custom display like this:
<my boxset name> • <genre>
e.g.
"Charles Mingus - Original albums • Jazz"

I tried with a tagFormat:
BoxSet.displayFormat={$BoxSet$Genre^^^ • }

when I try and save the config I got the error:
Incorrect option name 'display' in property 'tagFormat'

What is the correct way of doin' it?

Thanks a lot.

Giovanni, from Italy