Currently, recipe products are shown on tooltip only if the recipe has more than one products. For recipes that have only one product, it is not shown, mainly because their recipe icons can already describe the products, as discussed here with klonan: viewtopic.php?f=66&t=33732
By setting main_product to empty string, we can enforce display of products. But it is a hack and it brings another issue: it requires recipe name, icon, subgroup and order to be set explicitly because the recipe can no longer determine based on its product.
So, by adding another Boolean specialized for enforcing display of products, the problem will be solved. And we can even make a mod to let people choose whether products for ALL recipes should always be shown on tooltip.
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Edit: uploaded the mod so you can see the result: https://mods.factorio.com/mods/Mooncat/ ... e-products
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Edit 2: simplified the title