You can delete products either individually or in bulk.
To delete products individually:
Navigate to the Items screen and find your product in the Products table. Click on the product to open a product card.
Click on the 3-dots at the top corner of the product card and select Delete from the drop-down menu.
To delete products in bulk:
Navigate to the Items screen and check the boxes for products you want to delete.
A Bulk actions menu will appear at the top left of the table. Click on it and select Delete from the drop-down.

In both cases, Katana will notify you when a product is currently used on any open orders or Product recipes. Products can still be deleted even if they are actively used. On orders, a deleted item will be displayed with a strikethrough style (i.e. crossed out).