One option is to use the Transpose and Summary Tools. Here is an example tool layout and sample starting data:
There here is the configuration of the Transpose tool, notice that the fields that we do not want to concatenate are selected as the Key Fields, and "Dynamic or Unknown Fields" is selected in the Data Fields, these Data Fields will be concatenated together:
Finally will can use the Summary tool to concatenate the reshaped data, Grouping by the fields selected as Key Fields, and concatenating Value from the Add button String->Concatenate, also you can set the separator:
That will produce an output of:
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