You don't need a library of techniques. You need two or three you'll actually return to. None of these come with a guaranteed outcome, different bodies meet them differently. Try them, and notice what your own system has to say.
Coherent breathing. In for 5, out for 5, through the nose. Five minutes or more. Boring on the page; often the one people end up sitting with for the long haul. See how it lands for you.
Extended exhale. In for 4, out for 6 or 7. A different shape, worth feeling into and comparing.
Physiological sigh. Two short inhales through the nose, one long exhale through the mouth. Three rounds. Quick, portable, try it in the middle of a busy moment and notice what shifts, if anything.
These are invitations, not interventions. Daily practice is what turns curiosity into a baseline.