Multilevel hypergraphs are powerful and sophisticated structures having a great ability for representing complex entities and relationships at several levels of abstraction. They are a generalization of hypergraphs. We can use them for modelling graph databases, using multilevel structures for implementing hierarchical relationships between several graphs components and ensure inheritance between elements belonging to different abstraction levels. However, their complex organization demands a robust and flexible data structure having the ability to withstand any changes in its elements without compromising the overall integrity of the model. In this paper, we present and describe multilevel hypergraphs, analyzing their characteristics and practical applications, and specifying a set of CRUD operations especially oriented for the maintenance of their multilevel structures in graph databases.