You’ll need to spend a little more time on the forum before you are able to vote (when your forum “trust level” advances from new user to basic user).
Mods don’t mind merging redundant feature requests, but yes, spending some time to search for relevant topics may be helpful.
You can already do this using the existing custom field feature, but it must be configured manually for each site. If you would like assistance with this for a particular website, please post a link to the online form (you may want to start a new Ask the Community topic for this, though).
Alternatively, you may wish to support one or both of the following feature requests, which would bring more automation to the process: