I would like to have a total of just the charges on a liability such as a VISA card. Take out the payment data.
If you have your charge transactions also listed (double-entry style) in Expense accounts, and your payment transactions also listed in Asset accounts (eg your checking account), then I think a Cash Flow report will do exactly what you want.
Run the report via menu Reports, Income & Expense, Cash Flow. Then configure the report to show JUST the liability account: while viewing the report, go to menu Edit, Report Options, then in the resulting dialog go to the Accounts tab and select your liability account.
Using a Cash Flow report for a single account is something I hadn't thought of before but which I'll surely be using in the future, so I thank you for spurring the idea!