Board Thread:Theories and Speculation/@comment-26107879-20180520052942/@comment-27089028-20180520095322

If I recall Minato said the TSB's were not an activating out of nothing type but an always on standby type that undergo change in form. My working theory is that in order to create TSB's like Kaguya did you need to possess all five elemental nature transformations as well as Yin–Yang Release which is why Naruto is unable to replace the TSB's he lost during the war. So essentially you can create TSB's even though they're automatic as confusing as that sounds.