Retuning Glide
Changing a string's note while the harp is sounding used to jump it to the new pitch in a single sample, which put an audible click into a ringing string. Retunes now slide: the string bends from its old pitch to the new one over a short glide, the way a real string does when you turn its peg.
This applies wherever the pitch jumps while you are listening — changing a string's note, the Notes and Tune panels (Randomise, Reset, Set all to…), a note or fine-tuning stepping to a new value from your DAW, a single pitch-bend message, and the MIDI note modes. It deliberately does not apply when a whole sound is swapped underneath you: loading a preset, stepping through presets with ‹ ›, or reopening a session all land on the new tuning immediately, exactly as before, so presets sound the way they were made.
It also stays out of the way of anything you are already moving smoothly, because there is nothing left to smooth — you are sliding the pitch yourself. Dragging a tuning peg follows your hand rather than trailing it, and so does a pitch-wheel sweep and a fine-tuning automation curve that sweeps. The distinction is between a gesture and a jump, not between one control and another: the same wheel that follows your hand while you sweep it will glide if a single message throws it somewhere new.
The glide length is a parameter called Glide Time, which lives in your host's generic parameter list rather than on the panel. It defaults to 0.25 s and ranges from 0 to 2 s — set it to 0 for the old instant behaviour, or wind it up for a long, sighing portamento across the whole harp. Like everything else it can be automated.