The leftmost panel of Discover provides a hierarchy of package types -- e.g., "Applications" with "Developer Tools" and "Games" underneath, and various sub-categories (e.g. "Action" and "Arcade", under "Games").

However, this is only available when browsing ALL packages (both currently-installed and not-yet-installed). When viewing installed packages via the "Installed" option (at the lower section of the leftmost panel), there is no way to browse or filter by category. (Only sorting options are available.)

I think it would be handy to allow the same kind of browsing, but limited to already-installed packages (to help users answer questions like "what music players do I have already?", or "what was the name of that game I liked?").

It seems that only a handful of apps are currently listed as "Featured" in Discover.  I'm not sure if it's curated, or based on review feedback, but if this list ever expands, this same suggestion would be useful for the "Featured" software list as well.  (In other words, allowing one to view the current featured games, vs. featured graphics apps, vs. featured plasma add-ons.)

I could imagine this being done in a few ways:

 * Adding tabs at the top: "Featured", "All Software", "Currently Installed"
   * This would solve the difficulty I found in getting back to the "Featured" list (https://bugs.kde.org/show_bug.cgi?id=423343)
   * The "Installed" option at the bottom of the leftmost panel would not be needed
 * The "Installed" option at the bottom of the leftmost panel could act as a toggle (filtering the list to show only installed apps)
   * An option to view a top-level "All" category (to peruse all installed packages, regardless of category; as Discover does now) would need to be added