... and you can leave the names alone. They can be totally random (Sequential is for the Humans use, to help them put/keep things in place)
Names don't set the real order,
that is done in the
content.opf <spine>
in most cases, using Sigil to delete or rename is all that is needed. There are cases where cleanup fails to keep up completely and leaves
stale entries BEHIND (to be found by the validation tools
). The new entries are there, so the book works in many cases