Hi... thanks for responding.
I'm afraid I already have everything in the system trackpad preferences ticked (except 'secondary click'). I've been really very pleased with the transition to the new gestural trackpad which has come a long way since my old Tiger MacBook. The videos you refer to helped me 'tune-in', so adapt quickly.
Some apps authors have resolved the 'click-hold' action to 'tap + tap-drag'. In PhotoShop for example, the 'secret' doc info pop-up menu at the bottom of the doc window (bottom left, next to the scale) which I use all the time and has traditionally been a mouse click-hold action to view, does respond to the tap + tap-drag gesture.
After playing with the power zoom feature in InDesign however, the precise issue is that it is one of those 'click-hold' commands which does require a pause of a second or two in order to activate. This is why I think tap+tap-drag isn't resolving to it.. there is no room for a pause.
I'm trying to remember when I've encountered this before and can't, but feel it was the same - a 'click-hold+pause' action. I'm concluding there is no gestural equivalent so I've to resort to pressing the trackpad like old days... already feels antiquated, crude and jarringly inelegant on the new machine - quite something when you consider I've only had the new MacBook less than a month.
Thanks again. All the best.