Does the line being created with the Offset Line tool have to be in the same geodatabase as the line being referenced?
Answer
When starting an editing session and selecting the line being referenced, the Offset Line dialog will only give the user the option to select a template for a line that is within the editable geodatabase.
If the user starts an editing session in geodatabase A and selects a feature class from geodatabase B, a greyed out Finish button will appear when using the Offset Line tool.
Possible Workaround: Import the feature class into the same geodatabase as the referenced line.