Make diagrams with code. Compare this to the other tools, I find this method for drawing flow diagrams very helpful with regards to technical projects. There is tons of value in saving a diagram in a source version manager like Git and be able to generate the diagram. Additionaly, there are many parsers that come with other content management systems which render the UML. One example is using the macro in Confluence to render the UML as an image.
Below is a small example of code with its generated image:
@startuml a -> b: get b -> a: return json @enduml