By all means check with your docs, BUTT as mentioned it is an important area for nerves and biomechanical stresses.
The "transitional" designation likely refers to the physical anatomy of the vertebral bodies or processes themselves.
Lumbar vertebrae have certain characteristics and sacral vertebral bodies will have their own specifics.
When a lumbar has characteristics of a sacral or vice versa ... they are termed transitional
i.e. a little bit of both BUTT not quite 100% either / or.....
if that makes sense ?
transitional vertebrae can be a "normal" relatively common finding, and sometimes parts are fused together.
Unless they cause specific problems ... are just a notation on your file.
Cheers and Best Wishes