Finished implementing the ToolbarService that allows any module at loading to register its own ribbon tabs. All modules will define their tabs and will also catch the commands from their own registered tab.
Added at the Modeling module code that inserts a RibbonTab at loading. Here encountered problems that tabs from a designed Ribbon can't be taken and registered to the main Ribbon, had to define tabs in XAML as independent components.
Will continue working at connecting the buttons from tabs to launch SCSF commands in the modules. Probably will create a CommandService to make command connecting task easier and simpler for the developers.
A screenshot with the latest GUI improved by my colleagues: