This article details how to use a previously initialized TREZOR with Electrum. Your TREZOR must be setup before use with Electrum.
Plugin your TREZOR and open Electrum. Select Create new wallet and Hardware wallet. The Restore or import a wallet option is for restoring a TREZOR seed if the device was lost, stolen or damaged.
TREZOR is the only hardware wallet supported by Electrum and will be automatically selected in the next step.
Enter your TREZOR pin.
Input your passphrase if you used one. Any passphrase will create a valid wallet. If your wallet shows a zero balance, restart the process and double check that the passphrase was entered correctly.
You can now spend from your TREZOR with Electrum.
Even if the TREZOR is removed after use, the wallet will still be viewable in watch-only mode.