Explanation
Customize Customer Service workspace
You can use your browser's developer tools to customize some aspects of the Customer Service workspace.
Turn on the enhanced multisession workspace (preview)
* With Customer Service workspace open, press the F12 key to open the developer tools window.
* In the console window, type the following command and press Enter:
Xrm.Utility.getGlobalContext().saveSettingValue("msdyn_MultiSessionLayoutImprovements",true)
* Refresh the app page.
Note: If you turn on the enhanced multisession workspace, the enhanced experience applies in both Customer Service workspace and Omnichannel for Customer Service.
Reference:
https://docs.microsoft.com/en-us/dynamics365/customer-service/csw-overview#turn-on-the-enhanced-multisessi
https://docs.microsoft.com/en-us/dynamics365/customer-service/csw-overview#simplify-navigation-in-customer