Entering data in relation to another alignment should be easy - when you create a Linestring, one of the options where it normally says "Coordinate" is to enter data using Station and Offset in relation to another Alignment, this will allow you to enter a series of Offsets and Elevations to the reference Alignment to create your Footing, top of wall line etc.
When entering "jut outs" where e.g. the Offset changes from say -5' to -10' enter those locations with a 0.01; separation (in Station) i.e.
Station, Offset
0,-5
10,-5
10.01,-10
20, -10
Same applies in Vertical if you have Vertical Steps in the footings - but use 0.02' longitudinally for Vertical Steps
Generally TBC has a vertical Face tolerance for surface models (TIN Models) that says that they have to be 1/10 mm (0.000 328') (apart laterally, however the Corridor model has a couple of other tolerances that have to be considered so 0.02' works well (and there is a defect in this area that has been addressed and will be in the next release / update that we issue). This means that if you have a base of wall defined, and lets say you want a 10' high wall and it is vertical, if you create an offset line that is offset by 0.0004 or more (I typically use .01 or .005 to be safe) then you will be able to form a surface from the two lines to represent your vertical wall face. The offset effectively leans the face over slightly from vertical allowing TIN Modeling to work (if you still see flags in the surface, just offset slightly more and they should disappear.
So Use the Linestring Command as detailed above to create a Linestring using Station and Offsets date entry method above, and then having done that create a second line for the Top of the wall and a third offset for the Top / back of wall as necessary to create the linework that represents your MSE Wall. Now you can make a surface out of those lines that you can set to Color By Surface e.g. Grey so you can visualize it in your model.
You can also build this into a Corridor Model and tag the instructions that make up the MSE Wall Faces with Material Layer "MSE Wall Face" and then you can tell the Corridor to create you a Corridor Surface Model for Material Layer MSE Wall Face and you will get a second Corridor Surface that shows just those elements tagged with MSE Wall Face
In the above example I used the Linestring to create the base of wall, I then used Offset Line to Offset to crerate the Top and Back Top of wall lines and then made them into a surface model and colored it by Surface Color (Grey) in the 3D View.
Hope this answers the question Buck
Alan