Yes, I know that they are different networks, but a multicoin wallet like TRUSTWALLET wont let me send my TRC20 received USDT to the paxful ERC 20 uSDT address??They are the same USDT but placed in different networks?
No, It's impossible to do so in Trust wallet.
Binance allow you to select the network when withdrawing USDT. The reason is they are holding your coins in their own wallet and they can allow you to send USDT tokens on any of networks (ETH, TRON, Omni Layer, etc.)
Trust wallet is a non-custodial wallet and you hold your coins in your own wallet. If you deposit TRC20 tokens to your wallet, you only can withdraw TRC20 tokens. Also note for withdrawing ERC20 tokens from trust wallet or any other non-custodial wallet, you must have ETH in your wallet to cover transaction fee.