While i agree that it would be a bit cumbersome to have an extra button instead of just using LMB/RMB, i think mods like Angel's or Bob's could benefit from such a feature. Case in point, i researched "Chemical furnace" and cannot craft anything in it yet. And i have no idea how to figure out what to research to "fix" this (well, i could look inside the jsons myself, but...)
So in general, whenever an item (like an assembler or a furnace or even a boiler that turns fuel into steam!) has a recipe that references it at its "Made in" attribute, it would be nice to be able to see the list of such recipes. ^^
Actually, "what can be crafted in this thing?" could be part of a given machine's "Usage". Though to differentiate if it's a regnant or crafter, the given item could be highlighted in the "crafted in" section.