I’d like this too.
I hope to be corrected but the only way to manually add logins in Brave seems to be importing CSV.
You may try this: export your passwords (brave://settings/passwords, Saved Passwords, ⋮, Export passwords...) then open the file in a plain text editor, add a line in the same format (name,url,username,password), import back from the same menu.
Note that when I tried importing a malformed file nothing happened, not even a “syntax error” message, in case double check. Example:
example.com,https://example.com/auth/login,the-user-name,the-user-password.
edit: a word of caution: at least one user had a few passwords lost in the process.
I advise to write them down and double check both export and import, better safe than sorry.