Hello,
thank you for the explanation, and sorry for the typo in our previous answer: there is currently no keyboard shortcut for "Move document up" and "Move document down" in PDF24 Creator.
We understand the problem: the button "Merge all or selected documents" is right next to "Move document down", and one click merges all documents into one.
Thank you for the suggestion, we will add it to our list: a keyboard shortcut for moving documents, and a way to avoid or undo an accidental merge.