Downloaded apps disappear in launchpad after upgrading to catalina

ProgrammingProgrammer wrote:

Yes. I did that.

Try a SafeBoot https://support.apple.com/en-us/HT201262

  Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache,  etc. 

https://support.apple.com/guide/mac-help/open-apps-with-launchpad-mh35840/mac

You can try these steps to reset the Launchpad— (which is controlled by the dock).

• Make sure you’re in Finder or on the desktop.
• Click on the Go menu in the top menu bar.
• Hold down the Option key and click Library.
• Navigate to the. Application Support folder.
• Double-click on Dock.
• Delete all files that end in .db.

After that, restart your computer by clicking on the Apple icon and selecting Restart.

At this point, macOS should reset the Launchpad

ProgrammingProgrammer wrote:

That didn't help me. BTW, My mac performs a bit worse after doing it.

I would not be concerned here after the safeeboot, cache files will repopulate after use and you will be back to your normal.

See the Launchpad info provided above for your current macOS.

ProgrammingProgrammer wrote:

Yes that indeed works!

Is it possible to rearrange in alphabetical order.

Click on one icon in the Launchpad, hold down the mouse button and wait till they start to jiggle.

Drag the icons into alphabetical order— this is the only way.

The Application folder can be arranged in alphabetical order much easier.

You can always manually drag the missing apps from the Application folder to the Launchpad icon on the Dock.

Have you rebooted the machine?

Is it possible that you are talking about 32-bit apps that don't work in Catalina?