Hi Frank,
I remember some users were using directorist plugin with some success but I can’t confirm if that’s still valid to this day.
That’s mostly due to updates on both WordPress, GeneratePress and Directorist which may possibly introduce weird bugs that makes things unusable.
For now, the best thing to do is to try it out and see what breaks and then check what can be done with it. 😀
Note: Normally, if it works on default WordPress plugins, it should work on GeneratePress as well. If in case it isn’t, we try our best to have workarounds for any third-party plugins as we can but there’s simply too many of them. So we usually go by which is the most frequently asked plugin.