Simpler way of adding pre-defined knowledge bases

[reckart]

Is your feature request related to a problem? Please describe.
E.g. for layers, we have a nice Add button and when we click that, there is a great list of layer to be added to the project. However, adding a knowledge base is rather complicated - and that even though there are in principle certain pre-defined knowledge bases that can be added.

Describe the solution you'd like
A selection dialog similar to that for adding layers would be great to have for the knowledge bases as well.