Finally
! The last update (I'm on V Collection 8, but it has been announced as 9.2), Analog Lab 5.7 fixes slow preset changes between synths for me. I can now chain my songs in Ableton Live, change presets without having an intermediate Ableton scene dedicated to preset change! Maybe the tiny line in the release notes says it all: "Graphic performance improvements".
Before this one update, changing preset would take time for me when switching between synths, freezing Ableton, including my lighting track. As a workaround, I had to create empty Ableton scenes, so that I can change the preset without fearing a freeze of Ableton. Rest of the band had to wait for me. This is now over.
That's all. Just wanted to thank you.
Cheers from Grenoble.