With the new Unified Interface you may be finding it harder to locate the settings menu. When you know where too look it’s pretty obvious and makes sense but the first time it’s a little harder to work out the logic (unless you are used to SharePoint)
From the CRM web client, you can click on the cog and you will see there now new options there. One of which is Advanced Settings. When you click on this you will get the legacy Settings menu that you are used to.
UPDATE: Since writing this I have written a new blog on advanced settings which you can find https://wordpress.com/block-editor/post/d365lifewithoutcode.wordpress.com/21