Reasons why my component doesn’t show in the sidekick

In this case, it was a component without authorable fields, instead of having the display pull from a central administration screen. I write this hoping I’ll save other new developers a lot of time in the future:

1. In order for a component to show in the sidekick, it MUST have either a dialog or design_dialog node defined as part of the component, even if there are no fields. In this case, I suggest using the cq:editConfig node to remove the “edit” action and change the layout to “editbar” — thus providing a top bar to make the component visible but avoiding the author's frustration of no editable fields.
2. Add the component to a componentGroup that doesn’t start with a period. Technically, you don’t have to assign it to any group but you REALLY should as a best practice. Any component group that starts with a period will be hidden in the sidekick, not just “.hidden”. This is for organizational purposes, you could still have groups like “.hiddenHeader” and “.hiddenFooter” if you needed. Neither of these will show in the sidekick.
3. The component or its group must be enabled for a parsys on the page in DESIGN mode. Once enabled, it will show up in the sidekick but you will only be able to drag it to locations for which the component has been enabled.