DDJ SX3 Sorting buttons

Dear PioneerDj,
I don't know, if this is is bug or not, but I think that it is not working properly.
When I want to sort my library in Serato, I can hold shift and press one of the four buttons for loading a track to deck 1-4. But when I use only deck 1 and 2 and I use deck 4 for external input, I strangely cannot sort with load button for deck 4 to sort by artist even when I am holding Shift. The same goes when I use this deck for USB B. Can you please fix this? It will be great if would be possible to even MIDI map these buttons without holding shift, when users usually use only decks 1 and 2 and those buttons don't have any function. I am used to assign one button for Undo and one button for Autoplay. I am missing button for jump to search and button for switching panels (the button was on DDJ SX1).
Thank you for your answer