that's a difficult one. There does not seem to be a direct option for doing this.
But there is a workaround.
If this is the initial trellis gauge chart:
Then adapt it as follows:
Dimension: =if(aggr(rank(SA_RootCause,0,1),SA_RootCause)>0,SA_RootCause & chr(10) & chr(13) & Aggr(Count(SA_ID),SA_RootCause))
Now the title of each gauge is as before, with a page break, and then the value.
Below a screen copy
The format of the text is the same for the whole title. That's the limitation.
I really think that there is no other solution at this time. Maybe in a future version. (There is a similar issue with pie-charts in trellis, where only the last pie chart gets a Legend, so the Legend will often be incomplete for all other pie-charts.)
The normal solution ( Presentation tab, Text in Chart, ... ) only adds one text per overall chart.
In fact, it adds the value for the last trellis sub-chart.
You can see the relation if you press ctrl-shift when the chart is the selected window.