Is the only way to do live sampling of phrases on Digitakt really to open the sampling screen, arm and press play and then crop/save and place a trig and microtime until things are lined up as you played them?
I’ve searched and couldn’t find a satisfying answer, if that’s the only way might as well do everything in Ableton, which is fine, it just would be pretty sweet to have it all in the DT.
Can I interest you in an Octatrack?
Honestly, I don’t find the workflow on OT to be better enough / close enough to a DAW to be worth the desk space. 
Octatrack sampling is 1 button press or hands-off via rec trigs. If this isn’t convenient enough for you maybe check out the SP404mk2 that is constantly recording into a 40s skipback buffer. What exactly are you wanting out of a sampler?
I know some people, when recording in the sequencer normally, play through twice. It helps get the timing more on point when you don’t want to use quantize or are using a lower degree of quantization. Of course doing that, it’s basically an overdub so you only keep the second pass.
As long as your phrases can be contained within the sampling time limit, why not consider playing through twice, even if you have to shorten the amount you sample at a time. You may find it easier to trim and place a trig (less microtiming) from the second run through if the recorded phrase feels more in sync with the project.
Not questioning your ability play in time while recording, just from my own experience that feeling of “being put on the spot” where I have to punch in and record as soon as I’ve armed and pressed play leads to a less cohesive output. Whereas overdubbing sometimes feels more straightforward because you’re just letting it run and get more in the swing of it before you’re forced to commit, it’s the same idea. Would also allow for mistakes in the first run through without guilt or panic.
Anyways, wouldn’t hurt to try.
I don’t think there’s a great way to do it live on the DT. What you described is technically possible – just like it’s also technically possible to cook eggs with a hairdryer or to build a desk with a hacksaw 
Defined recording length is a game changer. No need to crop, which can be PITA, not precise.
You can trigger record start live with Threshold, but there must be silent before. You can even plock trigs before assigning the recording to active track.
Digitakt only misses a way to quantize recording start. Audio Threshold isn’t enough.
feature-request@elektron.se
Quantized start would be great. I would also be happy with an option to start sampling on sequencer start. Even better would be an option to also pre-record during metronome pre-count. I’ve sent the request into Elektron!
I consider this as quantized (basically). 
Would be also interesting after a pre-count. Better than nothing.
I hope you didn’t send a request just for pre-count recording without talking about quantize ! 
Do you use metronome pre-count in live situation ?
Honestly, I don’t see the point recording during pre-count, unless you want to edit audio.
Quantize start + pre-assign to active track = Looper for DT ! 
I was a bit disappointed they didn’t implemented recording start quantize with AR update…
Stockholm Octatrack syndrome ?
Oh! Yes of course. I tend to put alternatives in all my feature requests. I like to give them as many ideas as possible.
Actually what I meant by “live” in this context was sampling while the sequencer is playing, in my case I just would like to produce all on the DT without having to fiddle with Ableton. Maybe I should have said “realtime” 
Any solution that would help in the studio that also would happen to be useful in a performance would be fine by me.
Because the DT has OT-like machines now, Elektron must want us to see DT as more of a loop player than before, so it would only makes sense to let us record our own phrases without fuss. 
I tend to go to the essentials.
Yeah, see what you mean. I like to record at home as if I was on stage. With more mistakes and less pressure of course ! 
So did you try to make recordings with defined length and threshold?