If you are talking about adding products to the list of items produced and/or consumed by the MIN, then you don't need to edit the config.txt kuid table.
In the properties window of the MIN is a section labelled "Queues". Open that section and click one of the large "+" icons. You should then see a long list of products that can be added to that particular queue, and you have 6 of these queues available in the MIN. I don't know if there is a limit to how many items can be added to a queue.
For each item you add you will need to configure its starting quantity.
You will also need to configure the "Tracks" (load/unload, queue used), the "Processes" (how much will be produced/consumed) and the "Products" (vehicles loaded) - the latter is often hidden off the right edge of the properties window.
Of course, different MINs in your route can handle different products.
You will have to configure rolling stock to carry your set products and this may not be as easy since the creators will usually preset the types of products their wagons will carry so you will probably have to search for suitable wagons - after all, you would not expect a flat car to carry liquid loads.