Dialog is opened through the context menu - formats - matrix and from the elements menu. Change-Id: Ia1043e727d797998798ceb60322c6c42d402dce2 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/198166 Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk> Tested-by: Jenkins