I only know about these
https://tronsender.com/https://cointool.app/multiSender/trxI never had any experience with tron sender and if you are deciding to try this and you are trying with your own risk, im not suggesting you to try such multi sender app caused by the reputation was still unknown.
I know about cointool app but i don't know whether this is supporting tron USDT or not. You can check it by yourself.