Even if you're primarily making a game and not a general purpose engine it's really helpful to get some things out of text and into a visual medium. Usually in that case the tools are built into the game or a specific game editor. Examples are level editing, putting together animation, setting up assets for example transforms for character customisation and the biggie I've never not seen in a game runtime inspection of the game in progress.

All of this can be edited as text but it becomes laborious and error prone. Even setting up stats for something like an RPG is often better done in a spreadsheet where the results can be modeled.