If a Maniphest task has points assigned to it, this is currently shown as a TagView attribute on the workboard card when looking at the column view, which is very handy to know ('can I get this thing in the backlog done in a couple of days?'). This is shown along the list of projects/tags. Unfortunately, the same information is not immediately available inside the Maniphest query result view. This would make it more useful for developers who primarily work through this interface rather than workboards.
The immediate request which drove this was around filtering on parent task ID, i.e.: for this overarching parent task, have all its child tasks been estimated, and if so, what are those estimates? This helps show how long it will take to bottom out a large high-level task. It also helps drive the estimation process by making it more obvious which tasks are 'ready', and which need further estimation work to be done.
In an environment with lots of these high-level tasks, it is not feasible to use columns in the same way that #Projects and #Maniphest does (echoing T10187), so the workaround of grouping by column and use the points sum for that column is not practical.
I'm more than happy to provide the trivial implementation which I have working, but I appreciate this could fly pretty close to {T4863}, if the intention there is also to harmonise the information provided between the Maniphest query and Project workboard views (which would be nice).