I have encountered a bug in version 3.11.

Select "Add New Transfer"
Click on tab "Open Magnet Link"
paste in several info-hash strings
At bottom of screen it reports "0 links found" and the "Open" button remains grayed out.

ive tried adding magnet links through the add window with win 10, win 7, and linux and they all work.
are you sure they are proper magnet links?
what OS?
do other magnet links work?

same problem
bug happens when you paste info hash, not magnet
for example i paste "magnet:?xt=urn:btih:1234567892C6B685123456789DB4B1C9264B0685" - it works, "1234567892C6B685123456789DB4B1C9264B0685" - 0 links found
on 2.x version both options worked

Just a comment on posting..

When you post "a bug" it is better to specify what the bug is in the topic.

Crashes after some ten minutes if you have a huge quantity of complete torrents. Switches to "All transfers" each time you add a torrent causing the application to freeze.