Editing TIN: Adding/deleting triangles, moving TIN vertically.

I am learning V23 and there are some things related to editing TINs I would like to ask about:
a) Is there a way to change all TIN elevation at once? I mean raise or lower all TIN using some height value. The standard Move function seems to not working for TINs.
b) Is there a way to manually delete a specific TIN triangle? You can use the Delete Line function to delete sides, and so triangles too. But when you want to delete a specific triangle, you delete adjacent triangles too, if the side (line) is shared with another triangle.
c) Is there a way to add a triangle manually? I mean specify 3 points and make a new triangle. I have been trying to use the Add Line function, but it produces triangles in a way I don't understand. I would line to know if you can just click on the 3 points you want to form the triangle. Or alternatively, pick one side (line) of an existing triangle, and then the 3rd point of the new triangle.