It could be a new column type in itself, or just a formatting option of the existing Text column. But the idea would be to have multiline text box with as many options in a toolbar (like the one you have on top a created Section). This is particularly nice for when you expand the row and get the form layout where you could basically include some kind of Wiki in there (not just database fields, like Text which is way too basic for that)
Like for example, Notion takes this one step further and pretty much any record can be a page in itself. So you can keep drilling to write further pages on any row you need to. I guess that is a structural feature, but it would be great to at least write a rich text on any record if I wanted to.