Thanks for the very detailed answer! I may or may not take a stab at this if the person who originally asked for it decides that this is worth the effort.

In T15914#19057, @aklapper wrote:

Ctrl-clicking on the button opens the form in a new tab

@BlankEclair: Hmm, at least for the magnifier search button in the top bar search field that doesn't seem the case for me (Firefox, Linux). Do I misunderstand?

Edit: Ah, yes, it works with the "Search" button at the bottom of maniphest/query/advanced/, I see.

I haven't looked at Phorge's internals much yet, but perhaps the user could unmark a task as duplicate, or have the "Close As Duplicate" box be prefilled with the task that closed it and let the user deselect that and choose another one?

I was able to reproduce this on a test instance even though the task is closed long ago: