Put on rubber gloves and combine 1-part trisodium phosphate with 4-parts warm water in a bucket.
Dampen a clean cloth in the mixture and clean the surface of the Mahoney table, concentrating on the scratch. Allow to air dry thereafter.
Gently sand over the Mahoney table's scratch using 240-grit sandpaper to smooth it out, making it less visible. Wipe away any dust from sanding with a microfiber cloth.
Fill the scratch, if necessary, with wood filler using a plastic putty knife. Let the filler dry and then sand to make flush with the rest of the Mahoney table's surface.
Buff with wood oil soap using a microfiber cloth to finish and conceal the scratch. Use your Mahoney table as usual thereafter.