If you want to quickly mark all transactions as Cleared for an account without having to clear them all individually or per page in the Transaction Register, you can use the Mark All Transactions as Cleared setting to handle this quickly.
Settings at the top right side of the page, then click on Mark All Transactions as Cleared under the Miscellaneous Actions header.You will see an account selection form when you load the Mark All Transactions as Cleared page. By default, All Accounts is selected but you can select whichever account for which you want to clear all transactions. When you select the appropriate account, click the blue Clear all Transactions button.