The dialog to enter the PP doesn't have a reveal button. If you aren't sure then you could type it elsewhere and paste it in the dialog. The Password Manager (about:logins) can show the saved password and allows to copy username and password to the clipboard.

• https://support.mozilla.org/en-US/kb/password-manager-remember-delete-edit-logins

This extension enables you to see passwords entered on websites (not the primary password). You have to hide a password again before attempting to login.

https://addons.mozilla.org/firefox/addon/showhide-passwords/

You can modify this pref on the about:config page to make Firefox show the last typed character and set its value to a large value like 10000 milliseconds.

• about:config => editor.password.mask_delay = 10000

You can open the about:config page via the location/address bar. On the warning page, you can click "Accept the Risk and Continue" to open about:config.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Type/Paste editor.password.mask_delay in the search bar at the top of the about:config page. Double-click the editor.password.mask_delay line to enter edit mode and change the '-1' default value to '10000'. Press the Enter key or click the OK (✔) button to accept the change.