I am quite happy, how my kde on debian handles the theming for gtk apps like firefox or thunderbird. I usually use the
However, I use one application (moneyplex) that never looks good with my gtk theming. There are text fields that have ugly white backgrounds with light grey font color in them, where their background should be dark.
So I really want to set an override theme for just that one application.
I found a frequently named solution to try something like
and variants of it but it does not work at all. Is there any other environment setting that will override the current gtk theme engine for one app?