In this poster we will discuss challenges, requirements and good practices for creating synergies and inter-connections between national and international research and research data infrastructures from the perspective of the humanities. Stakeholders of the NFDI consortium Text+, of the German national node of DARIAH, of the SSH Open Cluster and of related EOSC projects are presenting benefits and outcomes of these structures and their linkages for the actual research data management and for the researchers. How are research data repositories connected and researchers guided to all the various service offers? With an example about the tool registry in the SSH Open Marketplace reused by Text+ and connected to EOSC, we illustrate the overall picture of these infrastructures and their impact in practice.