Can I change the 'Last Occurred' date for scheduled transactions

[vivire]

I searched and browsed the last year's mail
archive and cannot find any reference to changing
the 'Last Occurred' date for scheduled
transactions.

I am trying to enter a (sort of) complicated
transaction with variables and am tired of
retyping the whole transaction for each try (well,
I really haven't retyped it at all, seems like
there should be a better way).

Can I change the 'Last Occurred' date so I can
work with the transaction until it works the way I
want?

While I am asking... How are the variable fields
ordered in the dialog for completing scheduled
transactions? Can I influence the order at all?

I have very happily been using GnuCash 1.8.8 for
nearly a year now.