how to engage immobiliser, or if I should leave it off

[workingonit]

While I was having trouble with my dead diamond key remote repair, I tried to re-initialize it (unsuccessfully, since there was a loose trace inside the key). The "clowns nose" red light under the rear-view mirror blinked a couple of times, and nothing else happened.

I soldered the loose trace in the key, and it worked fine after that, but I've not seen the red light again. Is the immobiliser off or on? Since I only have the one diamond key (no other key), should I try to engage the immobiliser system or not? The key may malfunction at any time (from the damaged trace inside), and the system may not let me in.

I'm retired, at home 95% of the time, the X5 sits among several other vehicles & trailers in the "car paddock" behind my house (mostly hidden from street view, in my semi-rural area. Guarded by me full-time and my five dogs, it shouldn't be in much danger of theft (we're armed), though it appears to be the prime target among the "stable". Though, if I do drive and park away from home, I'm sure that an alarm may be a nice thing to have.

If the single diamond key will still let me into the X5, even if the remote goes unfunctional again (the embedded RFID chip should still be recognized), then how do I use/engage the immobiliser? I've read the manual, but it's still unclear.