I'm organizing all my seeds right now and deciding which plants will go where...can you plant kale, spinach, and 2 lettuce varieties together in a raised bed? They're all greens, so I would assume that's a yes, right?

Sounds fine to me.

That's great! Thank you!

Actually....
I wouldn't plant them together.... Different lengths of time required by each.
Sometimes when we purchase bulk seeds for the autumn garden, the seed salesperson will offer to mix turnips, mustard, and canola together.... And you can get away with that as they have the same growth times.

I'd plant the lettuces together, and plant the kale in a different part of the bed, and the spinach in another part of the bed.

Spinach is a slow grower, kale is generally a large plant, requiring being separated after the seedlings are large enough to handle, while lettuce is generally a fast performer...