Downloading Taskbar Tweaker 5.9.1. keeps on failing

What do you mean by "failing"? Do you see an error message? Can you share a screenshot?
Perhaps your antivirus blocks the download. You might want to try turning it off and turn it back on after downloading and installing the tweaker.

https://www.f-secure.com/v-descs/trojan-dropper_generic.shtml

I wonder if there is something wrong, or this is a false positive that could be prevented.

It's a false positive, and according to VirusTotal the detection is now removed:

https://www.virustotal.com/gui/file/0f1a062fcff547c3068caeb2c87a19b5c3165b33b58805c7cc707327cc987c45/detection

Thanks for submitting it to F-Secure.

Meanwhile I have submitted the (empty) file and origin to F-secure to see their reaction.

By the way, an update from your application without a separate download gave sort of the same result.

I had the same issue. I just downloaded the beta (5.9.1.1) and it loaded fine.

Yes, McAfee recognizes the installation as a virus.

I just tried the beta, though I don't know if I may even use it.

But anyway: same result. Still not accepted.