I had the same problem / constraint (not being able to add multiple tracks at once, with copy/paste) into Transmission... until I found a superb, awesome, Transmission client: Transmission Remote GUI. The interface is VERY similar to qBittorrent.
Latest version (as of writing this post) is 5.18.0
By the way, I am connecting to the Transmission app in my ...
When i first tried this, (I am as yet unsure as to why, BUT, it still may answer above question from another point of view) it was with one particular USB stick.
And when i followed, exqactly, Ubuntu's recommendations, and it would'nt show the iso, i scratched, my head, and thought why not try my other one.
The other one worked in exactly the way Ubuntu's ...
I had the same issue, and installed it the same way you did. I even removed it, and installed again, no joy.
I then installed over the top of the software store installation using the command line:
sudo apt-get install deluge
Now it works as expected.
Ubuntu 14.10 and Earlier
If your OS uses sysvinit, upstart, control Sync with the following commands:
sudo service btsync (command)
where (command) can be start, stop, or restart
Ubuntu 15.04 and Later
If your OS uses systemd, use the following commands to control Sync:
sudo systemctl (command) btsync
where (command) can be start, stop, enable, disable, or ...