I just found out with the help of @okh that it is not possible to input a value, say +5' (five feet), as an offset value in the X-Y coordinate fields of the Modify Wall dialog if application preference is set to Foot/Inch/Fraction.

You can see the discussion here:
Draw (offset) Wall from Existing Wall?

Why would this be available for Metric and Inch/Decimal but non-functional in Foot/Inch/Fraction?

Thanks in advance,
Delain