I have been reviewing the information on the 'Thomas Marshall's listed in this G2G made available in Anderson's The Great Migration Newsletter, Volumes 1-25. Boston: NEHGS, 2017. 'Marshall' is listed on pages 376, 511, 548, 551, 552, 558 and 788 (of the volumes). Briefly:
376 is an internal comparison of entries between the Register and the report
511-512 is on Problem Passengers and essentially discusses the difficulty of distinguishing between the two Thomas Marshalls and which is the accurate passenger. This was covered well above. Anderson reports that Savage and pope intermingled the records, while Lindberg and Patricia Law Hatcher have begun the disentangling process [TEG 16:158-69, 231-34; NEHGR 160:293-94]
548 Discusses freemanship for, probably, Capt. Thomas Marshalle of Lynn, who might be the Thomas Marshall who sailed for NE in 1635 on the James [Hotten 107; GM2:5:46-47]
551-552, 558...This is interesting: Discusses Thomas Marshall, who had settled in Boston by 1634 [GM2:5:41-46] was a supporter of Anne Hutchinson & John Wheelwright (what sinners!). Article states that Marshall didn't recant, but was not excommunicated. Bottom of 552 & top of 558 is a letter from Thomas Marshall dated 3 of the 9th 1643. It might be helpful to determine the accurate PGM based on which of the two were involved in the Hutchinson scandal.
788 top left starts out with Thomas Marshall being admitted to Boston church on 31 Aug 1634, eldest child born about 1727 indicating he was born say 1602 & would have been about 32 when he was included in this church list.
This information above might help determine which Thomas Marshall came over on the James. If there is still confusion, my own penny's worth would be to support S Willson's suggestion as to the adjunct box.