Declining a job offer without burning bridges?

The head of Cybersecurity from a company I worked at in tech support a few years ago (at the beginning of my career) has reached out to me saying they have a cybersecurity role that he thinks I’d be interested in and wants me to apply for. However I’m currently happily employed in cybersecurity elsewhere and love it, and don’t want to leave this job any time soon.

I’m wildly appreciative that I left such an impression that he thought …

career cybersecurity head job job offer offer role support tech tech support