Linux Diagram Editor. This plugin adds a dialog where one can define a diagram in this script. Once you will launch it you will notice that its tools window is also launched with it.
Dia can read and write a number of different raster and vector image formats. With this in mind it is possible to use efficient tools to make uml diagrams on linux systems. If you are familiar with markdown you should have no problem learning mermaids syntax.
Requirements the current dia release has been tested successfully on windows 81 8 7 windows vista and windows xp linux and mac os x.
Various icons templates are available for you to drag drop and edit easily. Diagrams can be exported to postscript and many other formats. Very easy to learn and use supports drawing many types of diagrams cross. The free edition is free for non commercial use and support everything you need in.