I practice a transcription that involves more elaborate jazz chords, modal sus9 and 13-chords, those kind of things, occupying many or all of the hands' fingers. I've played such things before (for instance, we did a cover of Robert Glasper's Better Than I Imagined) but failed thoroughly at the chords at the concert.
My problem is that these complex chords goes very slowly, with long time between the repositionings.
Theoretically I know what I play ("there's the 9th, there's a dominant", etc.) and I play without score after I've learned a section.
But it still remains, how do I get up to the intended tempo?
My answer is that the answer isn't fancy and there's no shortcut. Once basics are in place, push the tempo notch by notch together with the metronome (or perhaps no metronome).
Beyond that, what advice do you have to give me?