Does it matter if I put both types in standalone assembly and reference it in my CompositeC1 project.Standalone assembly if fine.
It also doesn't shows in console after application restart.If you by "doesn't show" mean that the Data perspective no longer show your type below "global data types" see http://docs.composite.net/Console/Static-IData-Types - you need to produce the tree. The easiest way is to use Tree Definitions.
The RelevantToUserType attribute will make your data type visible in selectors that contain data types, for instance when setting the foreign key type when editing a data type. It wont create any trees.