It's totally not related. If you were getting SSI, which is based on financial need, then yes, you would have to tell them. A lawsuit for an unrelated thing is the same as your spouse getting a raise, or winning the lottery, or getting an inheritence from your parents.......not any of SSDI's business.

SSDI only cares if you are working or if you collect public disability benefits.

And you're not a pain ! I didn't know much about SSDI 5 years ago when I was applying. Had a lot of time to read up on it during the 3 years it took to get approved. There aren't any stupid questions, always better to ask than to worry !