Open tax return-> Tools->Export Partners
Choose Special Allocations only. Give name for the file.
Open empty excel file. Then drag and drop the dif file to excel to open. If you click on the dif file itself, file will not open.
Update the file and save it as dif.
How to import back.
Go to Tools->Import Partners-> Special Allocations only-> Choose the updated dif file and finish the import.
If there were special allocation already in the system, it will not override the old allocation. It will add to it. If old special allocations need to be overridden, then delete it before importing.