When inheriting from an inner class, you need to use the full type, including the namespace

[Robert42]

This will have the Inherits: Table-Line empty:

namespace NS {

class Outer
{
public:
  class InnerA
  {
  };
  class InnerB : public InnerA
  {
  };
};

}

This workaround is necessary to get a complete documentation

namespace NS {

class Outer
{
public:
  class InnerA
  {
  };
  class InnerB : public NS::Outer::InnerA
  {
  };
};

}