There isn't an equivalent in workbooks for Splunk treemap, though this can be achieve easily within PowerBi (desktop version is free). This would be a great suggestion and I would recommend you raise it here https://feedback.azure.com/d365community/forum/3887dc70-2025-ec11-b6e6-000d3a4f09d0
May I ask that you mark the thread as answered, if I have answered the original question successfully and any additional questions get raised in a separate thread to ensure that other people can find the answers to the questions you ask easily.
kind regards
Alistair