@ColinT Welcome to the forum!
Bitwarden does have a feature to help with this. Open the login item to view its details, then click the eye 
icon to view the password. This will make available a new icon/button (with the numbers 1 2 3 arranged vertically). Click this 1 2 3 icon, and you will see your password in a form that has an index shown for every password character:
This can be used to assist you in selecting the 3rd, 5th and 9th character (Vrn in the example shown above).
Depending on how the bank’s login form is designed, it may also be possible to auto-fill the required characters by using custom fields to store the individual password characters (Edited to Add: See @danmullen’s comment here for more detailed instructions).