Family sharing: how to delete (hide) apps

How can I delete (hide) an app purchased by a child using Family Sharing?

My children need to ask parental permission using “Ask to Buy” before they can download any apps, whether paid or free.

Sometimes an app turns out not to be suitable (or just not what we need) and I would like to delete them permanently (and not allow the children to re-download them). With apps purchased using my Apple ID, I can have a similar effect by hiding the apps using iTunes (although it is not possible to delete them entirely).

I cannot work out how to do this with apps which were originally downloaded using a child's Apple ID with my Ask to Buy permission.