There are a lot of default devices in the device drawer, and you probably don't care about optimizing for all of them. For instance, you might want to focus only on mobile devices because another developer in your team handles the desktop website.
To prevent these devices from cluttering your list of available devices, you can disable them. First, click the Device Drawer button on the top left of the app header.
This will open the list of available and visible devices. Here, click the ⚙ Gear icon to open the device management window.
Here, enable or disable devices you want by clicking the checkbox to the left of each device, and save your changes.
If you want to remove custom devices instead of the default ones, click the Custom Devices tab on the top. Now, hover over the device you want to delete, click the 🗑 Trash icon to the extreme right, and save your changes.
Other than deleting, you can also clone or edit custom devices from the same window.