ITTF rules on draw/re-draws from ITTF 2018 Handbook (go to
https://www.ittf.com/committees/umpires-referees/documents/ and click on "2018 Handbook", direct link
https://d3mjm6zw6cr45s.cloudfront.net/2018/01/2018ITTFHandbook.pdf):
3.6.4 Alterations
3.6.4.1 A completed draw may be altered only with the permission of the responsible
management committee and, where appropriate, the agreement of the
representatives of Associations directly concerned.
3.6.4.2 The draw may be altered only to correct errors and genuine
misunderstandings in the notification and acceptance of entry, to correct
serious imbalance, as provided in 3.6.5, or to include additional players or
pairs, as provided in 3.6.6.
3.6.4.3 No alterations other than necessary deletions shall be made to the draw of an
event after it has started; for the purpose of this regulation a qualifying
competition may be regarded as a separate event.
3.6.4.4 A player shall not be deleted from the draw without his or her permission,
unless he or she is disqualified; such permission must be given either by the
player if he or she is present or, if he or she is absent, by his or her authorised
representative.
3.6.4.5 A doubles pair shall not be altered if both players are present and fit to play,
but injury, illness or absence of one player may be accepted as justification for
an alteration.
3.6.5 Re-draw
3.6.5.1 Except as provided in 3.6.4.2, 3.6.4.5 and 3.6.5.2, a player shall not be moved
from one place in the draw to another and if for any reason the draw becomes
seriously unbalanced the event shall, wherever possible, be completely redrawn.
3.6.5.2 Exceptionally, where the imbalance is due to the absence of several seeded
players or pairs from the same section of the draw, the remaining seeded
players or pairs only may be re-numbered in ranking order and re-drawn to
the extent possible among the seeded places, taking account as far as is
practicable of the requirements for seeding by Association nomination.
3.6.6 Additions
3.6.6.1 Players not included in the original draw may be added later, at the discretion
of the responsible management committee and with the agreement of the
referee.
3.6.6.2 Any vacancies in seeded places shall first be filled, in ranking order, by
drawing into them the strongest new players or pairs; any further players or
pairs shall be drawn into vacancies due to absence or disqualification and
then into byes other than those against seeded players or pairs.
3.6.6.3 Any players or pairs who would have been seeded by ranking if they had
been included in the original draw may be drawn only into vacancies in
seeded places