Use Account Code and or Account Name in journals
In the journal line you need two options to speed up large journals.
First - Coding based solely on the Chart of Accounts Code for example instead of typing 820 - Tax Payable there needs to be a Column where you enter 820. When posting journals in Xero it only relies on 820 and not the name.
Second - search for the account name and it populates the code.
Current Account coding is to slow for large entries of 300 lines.