I'm on latest v1.4 ATM and when I use the right-click -> set as browser -> ip:port:user:pass option the browser fails to work properly.
I tried updated Firefox and IE v11
The "use proxy" option gets set in the browser but there's no proxy entries in the browser settings. When I try to connect to a site I get 504 error and somehting about a subproxy not working.
When I set the browser manually to the same proxy it works OK.
For me this is not an urgently required fix or what have you but just so you are aware.