I have run into this more than once and wonder if there is a simple solution.
Open a design table in a new window to make changes. Have everthing done, great - looks good, exit to update SW, and have SW tell you that something is not valid, therefore we are dumping ALL your changes. Tough luck Charlie. Open it back up to fix the error, and sure enough, everything you had just done is gone. Am I missing the obvious other than manually saving a backup copy each time?
WT