I couldn't find something about it so far. As i tried to get rid of things waking my discs all the time galaxy came up in procmon.
It tries to create a file at D:\a01\_work\2\s\binaries\x86ret\bin\i386\msvcp140.i386.pdb about 350 times every hour. Thing is that this drive is for data only. No games, no programs and nothing game related is there and no directory structure like that. Therefore it fails and repeats.
My guess is that some annoying installer just tried to throw it's stuff on some random drive, messed up and didn't clean up the command queue.

Before i contact the official support i thought asking the community might help and saves some support time for other problems.

Question 1: How do i stop or fix this? Any kind of file where tasks to be done are stored where i could just delete it?
Question 2 (Bonus): How did this happen in the first place? I know some microsoft installer just throw their stuff on the drive with the most free space and sometimes 'forget' to clean up afterwards. But this is and was never the largest drive or the one with the most space. In fact it's the slowest, oldest drive in the computer and the smallest hdd. The last place where anyone should dump temporary data.

As an Example an event from procmon in csv:
"Time of Day","Process Name","PID","Operation","Path","Result","Detail","Command Line"
"17:39:17,9925664","GalaxyClient.exe","12112","CreateFile","D:\a01\_work\2\s\binaries\x86ret\bin\i386\msvcp140 .i386.pdb","PATH NOT FOUND","Desired Access: Read Attributes, Write Attributes, Synchronize, Disposition: Open, Options: Synchronous IO Non-Alert, Non-Directory File, Attributes: N, ShareMode: Read, Write, Delete, AllocationSize: n/a","""C:\Program Files (x86)\GOG Galaxy\GalaxyClient.exe"" "

That's from the Visual C++ Redistributable for Visual Studio 2015 package, so as you said, Microsoft's to blame for dumping the temporary files at random, instead of the system/user temp folder.

First,
1. Open Microsoft Visual C++ Redistributable latest supported downloads in a new tab.
2. From the Visual Studio 2015, 2017, 2019, and 2022 category, install both the x86 and x64 packages.
3. Restart your system afterwards.

Then,
1. Exit GOG Galaxy if it's currently running.
2. Open File Explorer.
3. Go to %AllUsersProfile%\GOG.com\Galaxy\storage\ in the address bar.
4. Move the jobs.db file to the desktop. If that doesn't help, move the entire storage folder to the desktop.

As i see it it's Galaxy trying to create the file. The Visual Studio runtime is just what Galaxy apparently tries to install.
Anyway, i did the install of the current package, rebooted, run galaxy and it was still there.
Then i closed Galaxy, moved the jobs file and tried again, no change.
Closed again, moved the entire storage directory and again, Galaxy trying to create that file. Change there was as no game is recognised as installed without the database ;)

At this point, I'd just go for a clean reinstall:
1. Back up the %AllUsersProfile%\GOG.com\Galaxy\ folder.
2. Uninstall GOG Galaxy from the Windows Control Panel.
3. Delete the %AllUsersProfile%\GOG.com\Galaxy\ folder if it's still there, and also delete the installation folder if that's left behind, which is typically C:\Program Files (x86)\GOG Galaxy.
4. Restart your system and make sure the issue is no longer occurring.
5. Install GOG Galaxy again using the offline installer (second link is for Windows).
6. Click the cogwheel in the top left, choose Add Games & Friends, then Scan Folders for GOG Games to add your currently installed games.

As for the support ticket, that's best opened sooner rather than later. It's not unusual to have to wait several weeks before getting the first response.