You have given me good advice, let me try to do the same for you. I make a giant Drink Mix for -Pre-Intra-Post Workout. The main supplements I use specifically for holding onto the muscle while shredding would be EAA's (better than BCAA cause it has the Full list of Amino Acids including bca's), L-Glutamine, Taurine.
If you go ahead and look up L-Glutamine and Taurine , youll see that they are known for its ability to help retain muscle and minimize muscle loss. Definitely has helped me, been in a deficit for the past 4 months. Other than those specific ingredients for holding on muscle, I also put in Creatine, Highly Branched Cyclic Dextrin, L-tyrosine, and Electrolytes for recovery purposes.