OmniOutliner Dark Mode

I have OmniOutliner 5.4.1 and OS 10.14.3.

It used to be that OmniOutliner had its own Dark Mode which came on if you had a dark document background colour. Now that I have a new computer with Mojave that doesn’t work anymore.

OmniOutliner does support the Dark Mode in Mojave but its own Dark Mode doesn’t work anymore. Is that correct or is there something peculiar to my setup?

OmniOutliner’s own Dark Mode is still described in the Help for OmniOutliner.

If I am correct that OmniOutliner has stopped doing its own Dark Mode, please can we have it back?