I found out that freeze delay and other elements here can also be done on the Digitakt (and in theory DN), with a midi loopback setup. A few things to bring back to ST for these tips:
FX “song mode”: 1/8 scale on the sequencer is perfect for sequencing effects scenes across a 32-bar song section (or longer with conditional trigs).
Freezer burn: the delay buffer persists after turning down delay volume. So it’s possible to capture a delay loop with one trig, seamlessly continue the song with a second one (Amp vol up, delay volume down), mangle the sound if desired, and bring it in later with a third trig (del vol up, amp vol down).
“Looper”: With the delay buffer running, you can add to it, of course. Turning up a track’s delay send will add new notes played on it to it, like a 1-bar looper. There’s no undo, so it requires perfect timing (or a keyboard with clock-synced arpeggiator).
Easier Freeze delay LFO numbers: with speed at 64, the LFO mult is the bar division (1x64= whole, 2x64, half, 4x64= quarter, etc; dotted notes are 4x48= quarter, 8x48=eighth, etc)