This is more a gameplay question but I am looking at how to make mods easy to understand without external docs.
When you have a custom reaction, and you do not have the reagents, you can press 'enter' to see details, what you need, etc. You can easily slip info there on the product names. Is there a shortcut to display such screen when the reaction is possible, considering that pressing 'enter' order the reaction to be done?
No. But it should be possible to display this ingame, maybe with a plugin like the ones Falconne makes.
I do use the workshop names and reaction names to give more info, for example each workshop has a reaction that says SKILL SOMETHING, and tells the player which skill the workshop uses. For very specific ones I add another with *description in here* as name, like "*100% chance to kill the worker*".
Other than that, no idea how to show more info ingame. I actually thought about a scribe workshop that can make a book. Like "Write book about Bloodbeasts", and the item will be "This is a superior leather book about bloodbeasts. blablabla massive creature, third cavern blabla, fight with edged weapons"...
Some sort of ingame manual that is written by the dwarves themselves. It would work, but of course its a lot to set up.
And there is the WTF text editor that can alter the ingame manual. You can rewrite it, to show a mod manual.