J'ai exécuté into this same issue and tried just about everything under the sun to fix it and ended up giving up and reinstalling. My friend recently ran into the very same issue (ONLY things from the new settings panel not showing in search results either from start search or directly from settings), and he said this fixed it for him:
%LOCALAPPDATA%\Packages\windows.immersivecontrolpanel_cw5n1h2txyewy\LocalState
First, assurez-vous Indexed\Settings folder is not empty. Vous devriez have a folder such as en-US (depending on your language) with bunch of files in there. If it is empty, vous devriez copy the files from another account or computer as described in the answer below.
Then, faites un clic droit sur the Indexed folder → Properties → Advanced → Check Allow files in this folder to have indexed in addition to file properties.
Cliquez sur Appliquer and Exit.
He said in his case, it was already checked, but he unchecked it → applied → rechecked it → applied and that fixed it for him.