Are you looking for a device type in the dropdown list of Ericsson.ATM by chance? If so, try looking for Custom.Ericsson.ATM instead. (Note: you can filter by setting the Vendor to 'Custom' first).
Failing that, try restart the CatTools UI again. This should refresh the device list.
Remember, you will also need to create a Custom.Ericsson.ATM.txt file (and drop in the \Scripts folder) too in order for the custom device to work.