It seems impossible to reduce the number of decimals displayed in the pie chart visualisation in Looker. It is by default 2 which is often too much and it would be useful to be easily able to change that, however even with the help of Gemini I cannot come up with a way to change it.
I tried to edit the YAML of the chart config but it went only from 25.16% → 0.3 → 0.3%.
This is a simple operation built in in Data studio and should be implemented in Looker asap.