Steps for updating the default currency
Turn on the Edit mode of your Looker Studio report. Click on the EDIT button on the top right of your report.
Now navigate to Resources -> Managed added resources -> EDIT
Click on Reconnect and continue.
Click on the drop-down arrow next to each field and choose the currency you want.
Click on Done.
Repeat steps 2 and 4 for the remaining data sources and click on close once done.
If the currency still does not change, try the below steps:1. Double-click on the metric whose currency you want to change. A new Chart menu will pop up on the right. Navigate to Setup>Metric and click on the small pencil icon.
2. Click on the Currency Type drop-down menu.
3. Choose the currency. You will now see the updated currency in your report.