Fedora 44 KDE
Tixati : 3.44.1

When one opens the file browser for what ever reason, like to select download path, or anything really, we cannot see the other partitions ( other than our system partition where fedora or any distro is installed).
So the problem is in the file browser itself, i think there multiple options to use and i have encountered this before in other softwares as well. To fix this is think you need to use the native file browser instead of whatever u have right now.

As you can see in the screen shots, My other partitions dont get listed in the other Locations as well.

https://ibb.co/4nr9j9p3

To be honest I think this is a problem with the file picker. Dolphin (KDE's default file manager) maintains its own list of favorite locations and file drives. For example, I currently have 4 manually added fav folders in Dolphin but the file picker used by Tixati only shows 3 of them and the latest is missing.

If you click "Other Locations" at the bottom, you should be presented a list of mountable and mounted partitions. It does show everything for me (Arch Linux). Have you installed Tixati in a sandboxed container of some sort like Flatpak?
I suggest you to forward this problem somewhere through the project's feedback venues. It deserves to be heard or bumped.