Great question — answering as the UphillTech team:
If they are set up with a plug at one end and a socket at the other, should be fine - though I'd certainly suggest plugging the 2A string into the 5A string, rather than the other way around.
Full answer by Ecnerwal: https://diy.stackexchange.com/a/53637 (CC BY-SA 3.0).
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