To create a preset, first set up your desired workspace by adding devices, choosing align modes, and setting zoom levels.
In this example, we've set up a workspace in Float Mode with a Galaxy smartphone in portrait, an iPhone and an iPad in landscape, and a custom device emulating a low-res 4:3 screen running Chrome. Each of them has a different zoom level.
To save your current workspace as a preset, click the ⭐Presets button in the toolbar, and select Save Preset.
This will open a popup window in which you can name the preset and select the settings that you want to preserve. Here, we're naming our preset "Phones, Tab and Desktop" and preserving all settings.
You can now see your preset in the ⭐ Presets menu. Click on the preset name to activate it.
If you've modified your workspace, you can switch back to your saved preset. Or, if you have created multiple presets, you can switch between them.