Hi laganc
To begin with, there are PowerCivil versions based on InRoads and GEOPAK.. which include different tools based on the source. So its tough :-)
You mentioned TINs... which is a GEOPAK term. So I will go with the thought you have the GEOPAK (the ORIGINAL) version of PowerCivil.
a) Composite Sections files (.SEC) are built from the Composite Section tool.
b) Transitioning is a "case by case" process. Typically, you will stop the first comp section short of the beginning of the second one.. and use the "drape elements" tool to define the elements between the 2 composite sections to provide a transition that you can control.
c) Batter slopes are a property of the Object you create - they are termed as Object side slopes. To set these, you edit the Object side slopes.
d) Vertical Alignment "tinkering" is achieved in one of two ways - dependant on how the vertical was created.
If the vertical is created as a COGO element, you would use the formal COGO vertical design tools, save the profile back to COGO and then update the Object.
If the vertical is defined using the "edit profile" tool, you would re-edit the profile and the update to the composite section and object would be automatic once the edit is applied.
e) Dynamic Cut/Fill calcs would come for the Analysis tools... it would typically be an Object to Object calculation between existing ground Object and your design Object,.
My responses are brief.... there is some level of expected knowledge required to interpret them. I did read you may be new to the software.
Touch base with the Bentley staff member Mike Barkasi (mike.barkasi@Bentley.com) and he may be able to supply a copy of the PowerCivil tutorial DVD that should explain most of the concepts and provide tutorials for most of the common design scenarios.
HTHs
Michael