When using third-party apps, beware, some of them create their own default wallet, different from a Trezor generated one. (For recovering such wallet you would need a recovery seed related to this wallet which is different from Trezor generated wallet.)
Once you initialize Ronin wallet, there is a default account(s) created (the red one in the picture). If you wish to use it, then you need to keep your Ronin seed phrase to recover and access this account whenever needed. This account is not a part of Trezor wallet.
On the contrary, there are Trezor accounts (the yellow in the picture). The same accounts are generated in MEW, Trezor Suite etc. These are Trezor generated accounts and can be recovered only by using Trezor recovery seed (and passphrase if enabled and used).
If you want to add another account connected to your Hardware Wallet simply click on the button (at the bottom of the previous picture). You will be prompted to export your Public key.
Please note that it is extremely important to have your Trezor device backed up .
The recovery seed is a crucial element for the security of your Trezor hardware wallet. If your device is lost, damaged or stolen, you can use your recovery seed to restore access to your entire wallet, passwords and other data associated with it. The process is simple; you only have to enter the words of your seed into your new Trezor device. (You may also use any other wallets or applications that use the same standard as the Trezor.)