[disclaimer - I work on the new build system]
That global list on the workitem is a mechanism that dated back to the original release of TFS. It's one that sort of worked in that day and age (days of nightly builds, pre-CI and CD agility). It's starts to fall apart and doesn't show as proper relationships in TFS. I worked on WIT at that time and we needed a queryable mechanism and that's what we had (blame me :)
So, when we started a new build system, we didn't want to rebuild things and repeat the same mistakes. We're trying to take an agile, incremental approach to a better build system.
In the next sprint (88), we are starting work on proper links between builds and workitems and the WIT team is also doing work to make them more first class. The first thing you'll see is a link on the WIT form and that should hopefully make QU1 as well (at least parts of it).
We realize this does leave a few gaps but we are working to close them (gated and label sources being two others) and hopefully in a better way for a better long term product.
As far as a workaround goes, it should be possible to automate via powershell and our clients but we don't have anything canned for others to use.