It sounds very much like you are under the impression Civi l3D is the next Land Desktop. It is in fact an entirely new product, not much of which is similar to LDT.
To be successful, you need to wean yourself from this mindset and read lots and take some training.
There is no description key file, it all done in the drawing. EVERYTHING is done right in the drawing. There are no external files like LDT has.
Prototypes...use different DWT's. Templates...in the drawing and are called assemblies. Symbol manager...use tool palettes, or the design center. Cogo blocks are wherever you want them to be, though they must ultilmately live in your drawing. There is no path for choosing them.
It's all about new learning my friend.
Matt
Matt Kolberg
SolidCAD Professional Services
http://www.solidcad.ca /