Is this something that everyone is experiencing, and if so is there a way to get the plumbob icon to appear?
No, I've been converting store stuff to packages since a while back. The icons disappear when you do this for some reason.I've noticed non-store items installed via the Launcher have the icon. Maybe the icon is supposed to mean custom content rather than store items?
That's not quite how it's working for me. All of the items that I downloaded with the launcher from the Sims 3 Store at least 100 years ago still worked in game prior to my moving of the DCCache files to the Package folder and have retained their plumbob, whereas any of my recent ill gotten gains and custom content did not show up prior to my moving of the DCCache files and have lost their plumbob.
I can only assume from this that any of the content which the game manages to load from the original DCCache folder keeps the plumbob even if the DCCache files are duplicated in the Package folder, but any content which doesn't get loaded unless it has been moved to the Package folder will lack the plumbob. I'm not close friends with the inner workings of the game though, so I could be wrong.