就 http://www.cantonese.sheik.co.uk/dictionary/characters/808/
[5] [prep] with regard to; concerning; as far as
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大的行李托运了
小的行李随身带着
The first part of the sentence stated the transporting solutions for the large items; the second part of the sentence stated the transporting solutions for the small items
- 就 as a preposition, connect the second part with the first part
大的行李托运了, - The large baggage items have been checked-in
这个小的行李(就)随身带着 - (with regard to) the small baggage items, (I) will carry them with me
Similar example:
你帶主力軍向東撒退 - you take the main force retreat to the East
我帶其他部隊向西撒退 - I take the rest of the army retreat to the West
你帶主力軍向東撒退, 我(就)帶其他部隊向西撒退 - you take the main force retreat to the East, (with regard to) I, (I) will take the rest of the army retreat to the West
You can see the role of 就 as a preposition (with regard to; concerning; as far as) more clearly in the following examples:
大的行李托运
小的行李随身带着
大的行李(就)托运, 小的行李(就)随身带着 - (with regard to) the large baggage items, (they) will be checked-in; (with regard to) the small baggage items, (I) will carry them with me
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你帶主力軍向東撒退
我帶其他部隊向西撒退
你(就)帶主力軍向東撒退, 我(就)帶其他部隊向西撒退 - (with regard to) you, (you) will take the main force retreat to the East; (with regard to) I, (I) will take the rest of the army retreat to the West
If we have 'if' implied in the sentence, then 就 would mean 'then':
(如果)大的行李托运, 小的行李(就)随身带着 - (If) the large baggage items will be checked-in; (then) the small baggage items will be carried with me
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(如果)你帶主力軍向東撒退, 我(就)帶其他部隊向西撒退 - (If) you take the main force retreat to the East; I'll (then) take the rest of the army retreat to the West
就 means 'then' only when there's a 'if'(如果) or 'since'(既然) implied before it in the sentence
In the cases of the examples in my answer, a '而' is implied
你帶主力軍向東撒退, (而)我(就)帶其他部隊向西撒退
In your previous question about 就, '等你来天津' (when you come to Tianjin) 'if' is implied