Re: Show title from selection in group (expresion) on chart
I am not aware of a way to do this, and tend to not use grouped expressions and rather inject expressions in with a variable and buttons to set that variable to the correct expression. You can then use the same button to set the title.
That aside, putting the expressions as you have them in a caption bar may seriously harm performance if you have a reasonable size data set. If comparisons are much less efficient than the Set Analysis equivalent and nesting these in the caption will cause all of them to be evaluated. I would recommend looking into whether you can re-write your expressions to use Set Analysis.