i'd also find such functionality useful. 

for now, it seems only epansion/reduction from the end is something developers had in mind. 

i try reduce a lv by specific exents - which also won't work with the current implementation ( see  https://listman.redhat.com/archives/linux-lvm/2023-April/026337.html )

i think this is probably the same class of missing functionality.  some more flexibility in addition and removal of extents without editing logical volumes at the raw level would be good  ( see  )