Hi Bastian,
Thanks for posting in our Community.
What button are you referring to? The 4 pads below the HOT CUE and ROLL button?
- You can get to the FX by pressing SHIFT and HOT CUE. These are the instant FX of djay.
- You can get to the SAMPLER by pressing SHIFT and ROLL.
Please note that you can customise the mapping of any MIDI controller. Just follow our MIDI Learn guides on iOS:
https://help.algoriddim.com/hc/en-us/articles/360016055199-How-do-I-configure-a-MIDI-controller-using-MIDI-Learn-on-iOS-
https://help.algoriddim.com/hc/en-us/articles/360016060800-I-already-mapped-this-controller-on-my-computer-Can-I-use-the-same-MIDI-mapping-file-on-my-iPhone-iPad-
I also encourage you to visit this thread, it has a lot of valuable information:
https://help.algoriddim.com/hc/en-us/articles/360014513500-How-do-I-MIDI-map-djay-Pro-AI-s-Neural-Mix-controls-
Let me know if you have any further questions.
Cheers, G