Just to clarify that the SmartThings IDE is part of the legacy platform (tied to Groovy) that’s in the process of being shut down as well. It does not use the new SmartThings API. You can either check the REST API directly or some people find a tool like the API Browser by TAustin to be helpful for this.
Based on what you described, it sounds like it’s a Custom Groovy DTH. That itself isn’t a problem – the problem is that Groovy DTHs could define custom attributes without defining them as part of a capability. In the post-Groovy world, SmartThings requires that attributes are defined as part of a capability and the new SmartThings APIs will not expose legacy custom attributes that weren’t part of custom capability.
The distinction is really critical. SmartThings is in the process of shutting down their Groovy platform and their new APIs fundamentally won’t show these legacy custom attributes (which makes sense since they’re in the process of completely shutting down Groovy). If you had joined SharpTools ~6 months ago, we were still using a Groovy SmartApp at that point in time and our Groovy SmartApp had access to all the Groovy stuff (including Custom Attributes that weren’t defined as part of a Custom Capability). But the new SmartThings APIs fundamentally don’t share this data.
In other words, there’s no going backwards. Only forwards. Either the Groovy DTH would have to be updated to implement a Custom Capability (kind of silly with Groovy being shut down soon) or you would need to migrate to a new driver like Mariano’s “Mc” drivers.
I understand that you’re in a bit of a limbo state at the moment as those Groovy devices haven’t automatically been migrated yet even though the Groovy SmartApps you used are already deprecated, but that’s the reality of the current state of SmartThings.