I’m a bit new to SmartThings and was planning to create new device handler for LAN/Other protocol in IDE but see no options for Capabilities. (along with other protocols BTW). Just in case I tried different browsers but no luck either …
The IDE is part of the old architecture, which will be going away soon. Most developers are now using the new architecture. And for that you use the CLI and API interface rather than the IDE. Or an Edge Driver if the connection is local.
but how long it will be available is the question. It is a groovy smartapp and at some point in the future, ST will end support for groovy on the platform.