What you can do is the following:
put your DeliveryNote in a dataview. In the dataview you can do two things:
1 you can show a list of Palette showing all available Palette's you have in the database (Source is From Database).
Then you put a microflow button in that Palette and with that button you can link the Palette to the current DeliveryNote (context object). That way you can always link Palettes. if you then add a second listview with all linked Palettes, then you know exactly which Palettes you have linked to your DeliveryNote.
If you really want to finish it, I would create a filter that would filter the already selected Palettes from the available PaletteList.
2. Create a button that will take you to a Popup page. in that popup you do the same as what I explained above, only you now have the available Palette's in a separate page. This makes it less confusing. So you don't have to display the already selected Palettes in that popup, because you do that on the main page. After selecting the Palette's you can link the Palette's to the DeliveryNote and you can close the popup, this can be done in one microflow.
I would start by focusing on getting it to work and then you can see if you can make it beautiful.
I hope this helps! good luck.