Enabling this feature
How to Turn on Bulk Deletion via User Type Settings
Next navigate to the "Inventory Access" portion of your user type settings and expand the menu. Scroll down to the “Bulk delete” permission and select either "Own", "Accessible Buildings", or "Any" to turn on the feature. Once you have selected the option you would like then go to the bottom of the settings and select "Save".
How to Bulk Delete Inventory
After you turn on this feature go to the inventory grid. Select the check boxes of the inventory items you would like to delete. Use the filter at the top to narrow down what is displayed. To select all the inventory items that are currently shown select the check box that is above the top inventory item displayed. Once you have chosen what you would like to delete select the "Delete" button.
Once you click delete, you will see a window pop up with a list of the inventory items you have selected and a checkbox verifying that you intend to bulk delete these items. You must check this checkbox in order to complete the bulk action.
Once you delete the inventory, you will receive a confirmation banner at the top of your page alerting you of the deletion of these inventory items is happening behind the scenes.