how safe is it to downgrade

[Qmag]

By downgrade I mean install an older version of Qbittorrent. The settings and lists that I use are very impotent. Is there a risk of losing it when I downgrade? I noticed that 4.3.0.1 still has the best performance.

[unseen19]

so install an older version on top of an existing installation/profile?
Yes there is a risk if the resume & configuration file structure are different. Save your profile containing these file first then you can make a try. The structure is not always different and others may have more intel to compare the version you mentioned and the actual one.

Nothing a backup cannot handle in short but be sure to have one

[Qmag]

Is it one of those, it either works or it doesn't situations?

[unseen19]

With different user profiles it may work (installed under a different user) but I've not tested.
Is a VM a possibilities on your setup? This will work for sure

[Qmag]

I'll just backup the settings and see what happens. I'm trying to revert back to qbittorrent_4.3.0.1 The newer ones are cause performance problems that I did not otherwise get.