Ability to add existing data as register columns

Would it be possible to add columns to listings making use of existing data that is not in custom fields? For example, the Customers and Suppliers tab listings include Telephone but not Mobile or Fax, yet Mobile and Fax are already built-in data fields.

There may be other places in the program where this feature would be useful, but these are the places that I find it would be convenient not to have to open a record with the Edit button to retrieve a number.

Similarly, it would be helpful to be able to list the debited and credited accounts in the Journal Entries listing, though that may be a more difficult change and is not so important, in my opinion.

I’m planning to get rid off many in-built fields such as Telephone, Mobile, Fax etc and simply replace them with custom fields which are now more flexible.

As for journal entries, list of accounts actually show if no narration is entered. If you are entering narration, I assume you don’t need to see which accounts have been debited/credited?

Actually, seeing the accounts might still be useful, especially if troubleshooting or searching for a transaction that went to a specific account. To be clear, I am referring here to the top-level register under Journal Entries tab. Obviously, the same information can be obtained by individually viewing the entries. So this is a matter of convenience, not necessity.

All my custom fields appear at the lower part of the page so removing telephone and the other defaults may misplace them on the page. Unless the user can precisely tell manager where to put the field.
Correct me

My suggestion only applied to register columns under the tabs. It was not meant to apply to invoices. I agree with @Abeiku that if information typically appearing on invoices is converted to custom fields, we must have the ability to specify where it appears.