Can anyone confirm if 5-pin DMX cable (primarily used for lighting applications) can be used as audio cable with no problems? For example, a run for an Audio Technica 835ST / BP4029? (with the add-on splitter to XLR3 at the recorder end)?

T.I.A.

No, you shouldn't use DMX cable for audio applications...

The cable used for DMX (110 ohm impedance shielded twisted pair) is different to your standard microphone cable (although it will still work, it's not ideal), but more importantly the pin wiring is unsuitable for what you want to do.

Standard DMX-512 connector (5-pin XLR) wiring is:

Pin 1 - Ground (shield)
Pin 2 - Data complement (Data -)
Pin 3 - Data true (Data +)
Pin 4 - Optional Second Data Link Complement (Data 2 -)
Pin 5 - Optional Second Data Link True (Data 2 +)

However, in a lot of cases pins 4 + 5 are not even wired - a lot of DMX cable only contains three wires inside the cable.

Yes, you could make it work with a bit of soldiering work - but you might as well just purchase some proper cable for the job...