The DDJ-FLX4 mapping for stems is here and it supports double-tap buttons to load stems directly like on modern NI hardware.
Mapping Link -
https://traktormaps.com/mappings/pioneer-ddj-flx4-stems
Load TAP = Load Primary (Stem Deck)
Load DOUBLE-TAP = Load Secondary (Track Deck)
Load HOLD = Generate Stems (hold for 2 seconds)
Note that double-tap is exclusive feature to Traktormaps mappings. If you download and try to distribute these features then give credit to original creator, thank you!
If you have questions, let me know.
