Yes but if you import each png to their respective layer, then you don't need the data because you're essentially rebuilding it.
However! I've just come up with an interesting technique that's much faster. If you're color correcting everything and assuming you're using a palette, then you can do something like this:
export the palette to an image of your current document, open the exported palette in photoshop, color adjust it, save and export it.
Now open a new Pyxel document (we need a new document to swap color with)
The size doesn't matter, so just press ok to whatever size you have. Import the color adjusted palette and save the document.
Go back to your tileset document and choose Extras->Palette swap, locate the document you made with the adjusted palette, and press replace.
If you've done it correct you should see a change like this.

The bad thing about this technique though is that you can't see the changes before you've applied it.