Concatenate Measures for Data Labels in Tree Map

Hi, swwong1 

Try to create a calculate column to concatenate Measures

_Concatenate column =
CONCATENATE (
    'DATA'[Client],
    "(" & FORMAT ( 'DATA'[% of Selected], "Percent" ) & ")"
)

Sample:

I changed your fields like this:

Result:

Please refer to the attachment below for details

Is this the result you want? Hope this is useful to you

Please feel free to let me know If you have further questions

Best Regards,
Community Support Team _ Zeon Zheng
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v-angzheng-msft 

Thanks for the above. I have looked into this and used COMBINEVALUES to join them together but as it was a measure, I couldn't add this to 'details' in the tree map.

In your solution, you have joined them through calculated columns but if you look at the % it is slightly different as I have 12 clients in total (but tree map only shows top 10). The calculated column isn't taking into account the filter context so it is showing the % of all 12 clients, instead of % of top 10 clients.