Using Mac-Sierra and LRcc. Most recent updates.
Unable to customize length on each slide. Adjustments I make in Playback module changes all slides. Have tried to select one or two slides in slide strip and change only those but does not work.
Is there a solution?
Sorry - no solution.
The slide duration setting is global, it affects every slide change. (unless you change "Manually".)
The Slideshow module is very weak in this respect, hence the reason I often use alternative software.
As wobertc as said, this feature isn't available in Lightroom and has been requested for a very long time.