The best thing I like in StarUML is that it is a very good software for drawing diagrams in a very easy manner for our projects.

The customizable options for desining domain models and activity diagrams. It has the symbols used in most (if not all) of the UML diagrams, but it also supports flowcharts, network diagrams, and a few other things that I've occasionally used as a software engineer. Also, StarUML checks latest updates and install automatically for Windows and MacOS. Finally, I love the touchbar functionality. It is easy and convenient to edit diagrams. If your UML Diagrams are getting too complex try breaking the digram up into several diagrams each of which covers a smaller subset of classes. You may even want to move your classes into seperate packages to keep them organised. In Star UML (and other UML Tools) classes can appear in more than one diagram so you can include all the classes from one package plus the classes from a differnt package's public interface.

The best thing about this tool is that it is very user friendly and very helpful in visualizing the requirement of the project in the graphical and hierarchy form. It also helps in creating different kind of models and determining dependenies between different elements of model. Also using this tool, we can perform dependencies test on model which helps in validating our model before finializing it.