How to invite user to organisation from organisation admin role?

We have several organisations, one of which has Admin user. This user would like to add invite users from main organisation (id=1), how can I allow it without giving Global Admin role? According to documentation there should be a way, but I could not find a way.
We use Grafana 5.2.4

In org users list there is a invite button


There is none for local org admin, but it is for global admin.