Blueprint UML Editor is a modeling tool that makes it easy and quick to create UML2 diagrams.
You can create the following diagrams:

Structure Diagram
Class Diagram, Component Diagram, Deployment Diagram

Behavior Diagram
Activity Diagram, Sequence Diagram, Communication Diagram, Statemachine Diagram, Usecase Diagram

Please check the support page for the elements that can be created in each diagram.

You can also color, align, and rearrange the elements.

The appearance supports two types of themes, light and dark.