We have implemented a discussion URL section in the proposal details page
We don’t want the proposal creator to be able to specify this because a direct link from the dashboard page could be perceived as being endorsed (and as a result can be used for malicious purposes). The currently implemented solution is for a “trusted” address to set these URLs, which obviously comes with its own issues.
As a result, we decided to drop the “discussion URL” section. You can create the forum thread with the label “Official Proposals” on this forum (or anywhere else you’d like), and link to it in your proposal description. The user should know that all URLs in the proposal description are from the proposal creator and use them with care.