OSX disk space shows 200GB as "other" I have a Macbook Pro Retina 13" Mid 2014, with a 500GB disk. 

I never have to work with large files such as movie editing or anything like that nor do I use time machine backups. After upgrading to Catalina 10.15.4 I noticed my disk shows ~200GB of used space which I have no idea where is it coming from.

Rebooting doesn't help and even the system information tool is not giving information on what's taking up that much space.

In the image below, the other sections (Applications, Documents, etc) all contain the correct sizes that I expect from the stuff that I use.
You should run DaisyDisk on your mac. It will give you a graphical mapping of all the space on your drive. The app is about $10, but has a free trial you can use. Just download it from the link.

There is also an older version names Disk Inventory X which is Donationware. It says on the link:

Disk Inventory X is a disk usage utility for Mac OS X. It shows the sizes of files and folders in a special graphical way called "treemaps". 

If you've ever wondered where all your disk space has gone, Disk Inventory X will help you to answer this question. 

For a quick start, please read the readme file on the disk image. Or see a 1 minute video about Disk Inventory X from macbreak.com. 

Both apps take several minutes to scan your disk.