Make FileVault password different from user login password?
No. However, you can set up a second admin account.
Any admin user/password can be used to authenticate graphically so you could do something insecure like make an account user and password with me/me.

Shift tab, change your name to me, then tab and enter me again for the password and press enter.
What I’m doing is using fingerprint or devices like yubikey or my Apple Watch to unlock but what I have nearby as opposed to what I type.

https://www.yubico.com/us/store