Gotta Set up Custom Fields for those things, and they should work. Search for Custom Field and make note of the Ctrl-Shft-J combo to open the HTML Elements screen, where you can find the actual name to use for your Custom Field.
To clarify your request, are you asking for an automatic auto-fill (when the web page has been loaded in your browser), or manually triggered on demand?
It is very lacking not to have this feature on Android. No ability to fill out forms from identities in Bitwarden without copying and pasting each field. Poor user experience here!