You’ve shown that the Item exists under Items.
You’ve shown that the Item exists in the Developer Sidebar.
You’s shown that the Item exists in the auto-completion dropdown.
So I think it’s pretty safe to say that the Item exists.
Even though you are an old hand with OH, definitely review the Getting Started Tutorial, in this case pay special attention to the Semantic Model. There is a lot of useful information there including
However, the model is not intended to represent all your Groups and Items…
Existing Items can be added to the model. Browse to the Item in the Items settings, click on Edit and choose an appropriate Semantic Class and Semantic Property. Then add the Point as a member of the appropriate Equipment or Location Group. If the Equipment Group doesn’t exist yet, create a Group and use the appropriate Equipment semantic tag first and add the Equipment to the appropriate Location Group.
If your Item doesn’t appear in the Model view then it has not been tagged with a semantic tag and therefore is not a part of your model.
Note that the above assumes the Items are managed. If they are defined in .items files you’ll need to add the tags and set the Group membership there and not through the UI.