Thanks. Go to Preferences/Controller Manager and look in the Assignment Table. Scroll down the "Assignment" column and change every Deck A to Deck C, and change every Deck B to Deck D. Save yourself some time by ignoring every line that has "n/a" in the "Mapped to" column.

It's possible the S4 mapping is conflicting with the Touch OSC mapping. Try disabling all other mappings except Touch OSC. It might be possible to have S4 and Touch OSC mapping run at the same time, but you need to check in/out port settings in Preferences/Controller Manger/Device Setup.

Yeah sure but I made this mapping about 18 months ago and I've kinda forgotten how Touch OSC works since then! Before you get started, make sure that Traktor and Touch OSC are connected via midi. I modified my tsi file from an official Denon mapping so it actually includes commands for 8 hotcues across 4 decks. I only assigned 4 hotcue commands across 2 decks but the remaining commands are still contained within the mapping, they're just not assigned yet. This is good news for you. Go to Preferences / Controller Manager and make sure "Raycotek iPhone/TOUCH OSC" is selected in Device. Scroll through the Assignment Table until you find "Select/Set+Store Hotcue". There are 32 of these commands (8 per deck). If you click on one of these commands, it will tell you which Hotcue it refers to (Look at the bottom of the screen), which deck it's assigned to, and which button it is "mapped to", as well as other info that you don't need to worry about. Let's say you want to assign Hotcue 5 on Deck A to a button on your Touch OSC design, then find the "Select/Set+Store Hotcue" command that is Set to Value HotCue 5 on Deck A. Click Learn and then press the Hotcue 5 button on your Touch OSC device. The Device Mapping in Traktor should read the midi signal from the device and set itself automatically. Click Learn again to turn off Learn mode. Hopefully you have just mapped Hotcue 5 in Traktor to the Hotcue 5 button on your device. You'll need to do that for each hotcue on each deck. Most controllers work like this but I honestly can't remember if Touch OSC works in Learn mode. If not, you'll have to assign the midi value manually. Once again, find the "Select/Set+Store Hotcue" command for Hotcue 5 on Deck A, then click on "n/a" in the Device Mapping and choose a value like "Ch01.CC.xx" where xx is the unique midi value of the button in Touch OSC. You should be able to find that info from somewhere within the Touch OSC interface. Give it a try and if you can't make it work, let me know.

I managed to customise a decent mapping suitable for my iPhone 5. Thanks for the advices.