Foundry VTT v14+

Spellcraft is a system for inventing, modifying, and discovering spells through dedicated research, built for D&D 5e.

Read it at spellcraft.wizzlethorpe.com.

It is also a Wizzlethorpe Vault, so you can pull the whole system into a Foundry VTT world. Pages become journal entries, the roll tables become real drawable RollTables, and internal links become clickable journal links.