By default, each transaction is treated individually. When you move the mouse over the upper right corner of each transaction, buttons that can be edited and deleted are displayed. On mobile, you can access the menu by clicking the pull down button in the upper right corner.
In the transaction history, click and drag as many times as you want with the mouse to select the range. Or click one by one empty space in the transaction to include or dissolve the selection. Likewise on mobile, you can select multiple by clicking on an empty space. Multi-selection is possible up to 60 at a time, and after selecting, you can batch re-enter, batch edit, and batch delete using the management button that appears at the bottom.