Version 13 mainly focuses on the GUI. MeldaProductioin to improve the clarity and ease of use. The GUIs themselves have been redesigned when appropriate and some related changes have been made.
There's a new style (Neon), which is now the default style and everything is designed to work well with this style "out of the box". This includes everything from basic components to various graphs and analyzers. Previous style settings are ignored now. If you feel the need to get your style settings back, it is not recommended, but you can hack the engine by going to the user settings folder (where the presets are) and copy StyleSettingsV11.cfg to StyleSettingsV13.cfg in proper folders. Note that other styles may not work that well compared to Neon. While Melda is going to improve other styles slowly as well, it has a low priority. Neon is the new "look" of Melda plugins.
All MeldaProduction plugins are provided with 15-days fully working trial version. Download them and try the new GUI.