All visual recipes in DSS operate on the full data, so without sampling. The sampling we apply when you visualize a dataset or work on a visual "Prepare" recipe is only for you to be able to prototype and understand your data quickly. But when you actually run a recipe, it is applied to the full data.
Hence, if you create a "Group" recipe, taking the sum of "transactions" by "ID", it will perform what you want. From your example, I understand that you want the output of this group recipe to be "non-partitioned". Make sure you select this option when creating the output dataset.
Then, make sure the partition dependency setting is "All available" in the Input/Output tab of your Group recipe:
Note that if what you wanted to perform the sum of transactions by ID separately on each partition, you could do that with a partitioned output and the "Equals" partition dependency setting in the screen above. If you plan to work with partitions in DSS, I encourage you to read: https://doc.dataiku.com/dss/latest/concepts/index.html.
Hope it helps,