To add inserts to a drawer, such as trays, racks or mats, follow these steps:
Select the drawer to which you wish to add the drawer insert, and navigate to the Drawer section in the properties panel
Open the 'Customize' panel, and therein, open the 'Drawer Accessories' menu.
Against 'Drawer Inserts' select Add.
In the carousel that opens, select the thumbnail drawer insert you wish to put inside the drawer.
That accessory will adjust itself the drawer's internal space.
Note: In the event that there are no drawer inserts in the carousel already, you will need to add them from the Infurnia Warehouse. Refer to the article below,