I'm currently trying to modify an existing line to be offset x distance from another existing polyline, is there any tool/addon that does that? I currently use Copy Parallel and create a dummy line that I move/snap my line to. I was just wondering if there was any way to directly specify that I want an existing line to be offset parallel from another line x units.
Within the editing tool bar you can also create a new feature and specify the angle and length of the segment.
If you have the COGO editing toolbar available to you there is a tool called: Offset Line you could also edit your sketch properties by +/- the specified distance (more math).
The Copying Parallel Features might be of interest to you. From the help: "Copy Parallel makes a copy of selected lines at a distance you specify. You can choose to copy the new lines to the left, right, or both sides of the selected lines. You can use the Copy Parallel command, for example, to create a street centerline or a gas line that runs parallel to a road"