These functions already exist:
Press and hold the VIEW button to tag a track.
Press SHIFT+BACK to open the Playlist Palette; pressing it several times will toggle between the 4 palette views, the 5th will close it.
No, there is no direct shortcut available - but you can always dump your House playlist into one of the palette windows and it will remain there even after closing / reopening rekordbox. You can store 4 playlists per palette for a total of 12 that are always just a button-press away.