I'm sorry if this has been answered elsewhere; I tried to look for this issue on the Wiki and in the forum and didn't see it.
This is a fairly trivial problem, but it is annoying. It has been happening ever since the earliest beta of Catalina, and I had hoped that once the final release was out, it would either be fixed or a Transmission update would come out that would fix it.
The problem is this: when I click on Magnet links, Transmission opens a Save dialog box asking where I want to save the downloaded file, even though I have specified a default save location, and after I dismiss this window, ANOTHER Transmission dialog box opens showing WHAT I am trying to download, with options to (re)designate a Download destination folder, specify Group and Priority, and a checkbox to "Start when added". I have tried modifying all of the preferences for these particular behaviors, in the hopes that simply tweaking the settings would fix it, but this hasn't worked. I've also deleted the .plist file and re-configured all the preferences, which also has not worked. Also, I have the "Watch for Torrent files in" folder specified as my Desktop folder, but it doesn't work. If I download an actual .torrent file, I have to manually double-click it in order for Transmission to start it. Oddly enough, .torrent files DO NOT invoke the two dialog boxes that magnet files do.
I am using version 2.94+, and recently updated to the latest nightly build, but the problem persists. I never had any of these problems prior to Catalina, and I'm not having them on my other computer, which is only running El Capitan, same version of Transmission.
I know these aren't important problems and I was hesitant to even post this, but I figured I'd just give it a try and see if it was a known issue or if/when a possible fix might be in sight.
Otherwise, fantastic problem, I use it all the time and love it!
Thanks,
Pete