Hello all, I think I found a certain way this can be accomplished, For example if the field is long and there is an identifier in the field like an "-" or '_' you can use a subfield expression in the data model to break out the long field into 2 fields. Then take the two fields in your chart and create a calculated dimension like for example : [Field1] & chr(13) & [Field2) to create 2 rows in your specific field. I tried this an it worked for me! Hopefully this helps!
I thought that you are talking about the values on X-Axis.
If this is the case, using settings legend (from Presentation) would not help. Instead you have a possibility to use ”truncate label “from X-Axis tab. If a “pop-up label” is checked then you could use the pop-up text to view the long name (see attached).