No field to update password in Mac Settings 'Internet accounts'

Correct. You change an email password in the Mail app.

Zhuleea wrote:

my Mac is on Sequoia 15.3.1, mail account's password field not present

Luis is correct. IMAP mail passwords can be changed in Passwords.

I am seeing the password field in Internet Accounts for a POP password, but not for other accounts.

I don't see any option for changing passwords in the Mail application.

Some passwords (including my IMAP mail account passwords) can be changed in the Passwords application.

Just to add, you can also change your email password on your email provider's webpage. Then the next time you open Mail it should ask for your new password.