Complex sentence: They were assisted by Betsy Hall, who worked as scenic designer from 1953 to 1976 and Tom Vawter as scenic designer/T.D. from 1976 until the mid 1980's.
Split into simpler sentences: They were assisted by Betsy Hall, who worked as scenic designer from 1953 to 1976. Mr. Tom Vawter also acted as scenic designer/T.D. from 1976 until the mid 1980's.