Once a device shows “placeholder” in the IDE, you should no longer change the device type handler through the IDE or you can break communication with the device.
That’s because the IDE is part of the old groovy architecture and devices showing “placeholder” are using the new architecture.
So, yes, you have to remove the device from your account and re-add it to pick up the custom DTH.
Also note that once a device is using the new architecture, other information in the IDE, including the routing, may be incomplete or incorrect.
See the community FAQ:
FAQ: Why does the IDE list “placeholder” for my device? Can I change that?