Creating suitable diagrams for technical and scientific publications is challenging and time-consuming, as manual control over the layout is required to communicate information effectively. Existing diagramming tools usually allow modeling the diagrams via a textual domain-specific language (DSL) that can be rendered and auto-layouted or via a graphical editor. While auto-layout is fast, the results are often not satisfying for most publications. However, graphical editors are time-consuming to create large diagrams. The blended or hybrid modeling concept enables creating diagrams efficiently using a DSL and editing the rendered diagram via the graphical editor for fine-tuning. However, hybrid modeling editors are limited to individual diagram types and do not save the layout and style information in the textual description. Therefore, we propose HyLiMo, a hybrid live-synchronized modular diagramming editor. In HyLiMo, diagrams are modeled in an internal DSL and live synchronized with an interactive graphical editor for the rendered diagram, allowing a straightforward layout and style change, which is stored in the DSL code. HyLiMo is independent of specific diagram types, but we offer specific functionality for UML class diagrams. Using the language server protocol, we implement it as a web app and IDE extension. The results of our user study indicate that such an approach enables fast and precise diagramming.