non-technical answer: the IDE is part of the old groovy based architecture. It will be going away, probably before the end of 2021, and be replaced with something else. in the meantime, anything which is using the new architecture will be represented in the IDE with “placeholder“ under the device type column. This includes devices using an Edge Driver. Since new edge drivers are being added overtime, it may even be that a device which is the same model number as a device you previously added which used a groovy DTH is now using an Edge driver and so shows up as placeholder.
Don’t change it! Once the device is using an integration from the new architecture, you can no longer get to its code details through the IDE, And changing it to a different device type may break the integration altogether.
If you need to change it back to a groovy based DTH you will probably have to first remove it from the integration. But the details of that will vary depending on the exact device, so go back and look for the information on that integration.
There are some devices which may have a choice between using a groovy DTH or one of the placeholder integrations for a few months before the integration is complete, but you can’t switch between them just by changing the device type in the IDE. You will probably have to remove the device from your account and add it back in using the other method, but again, that will depend on the specific model.
So if you see a placeholder entry, don’t worry: that just means it’s using the new architecture.
(Warning: as @johnconstantelo notes below, as of this writing you are no longer allowed to add a device through the android app if it would bring your count above 200 devices at that location even if you already have more than 200 because they were added before this limitation went into effect. )