I don't know why, but I have vivid memories of there being an in-editor palette editor, but after checking older NSMBe revisions, it seems to never have existed (I'm using the latest version, b379). Basically, it would allow you to change palettes within the editor. You'd click on a colour, a colour wheel would pop up, and you'd pick which colour you want. After picking, it will replace that colour in the palette. This wouldn't change the whole palette, only that colour.

I find that this could be useful for many reasons, mainly jyotyu editing and recolouring. Instead of importing a new image with a different palette, and possibly screwing up other things that use that palette, you could change one colour and be done with it. Same order, except that one colour is now different.
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Check out "New-ISH" Super Mario Bros. DS HD*!!
Renewed Super Mario Bros. still exists, though.

I remember it too, but I think you need to hold [Ctrl] while clicking the colour.

Oh, so it does exist! Holding [Ctrl] while on a palette colour does bring up a menu! I think this info should be mentioned somewhere, but I don't know where.
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Check out "New-ISH" Super Mario Bros. DS HD*!!
Renewed Super Mario Bros. still exists, though.

holy shit I had no idea. I thought I knew everything there was to know about the editor.
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Nothing to say, so jadnjkfmnjamnfjkldnajfnjkanfjdksan jsdnvj m.