To rephrase your request... You have this:
Which from the console yields this:
You want a data element that will return your sku(s) and another that will return your quantity(s), etc.
The problem is really that DTM data elements can hold anything but the DTM UI (for Adobe Analytics and other tools) resolves data elements into strings (and will choke on complex data types that cannot be coerced into strings (thus [object%20Object]).
You CAN access individual array indexes in the Path field of a JS data element, so you could get at the 1st, 2nd, 3rd sku with three data elements using:
...but this is dumb (and probably not what you are looking for).
If you need to iterate through the items of transactionProducts you'll need to do it in custom JS.
What is your end goal? Are you trying to get this data into Adobe Analytics? Into Google Analytics? Into 3rd party tags? Other?