On top of the Enter Coins page, you can delete trades individually, grouped or completely.
If you select just one trade by ticking the box, a delete button appears. If you click on Bulk Edit/Delete, you can delete all trades as well as bigger groups of trades, eg. selected exchanges, dates. transaction types etc.
You can also select and delete multiple trades at once in the trade table on the Enter Coins page using the SHIFT (range select) or CTRL (single select) key on your keyboard. This is limited to 50 transaction at one time.