Microsoft has made really easy for Windows 10 users to point out problems and give suggestions to the Microsoft team working on Windows 10 via the Insider Hub app. You must signup for Microsoft's Insider program to give the feedback.
This is how you get access to the Insider Hub.
Search for Insider Hub.
Once you click on the Insider Hub, you will see it will open the following app. If you're not logged in to Windows, it will ask you to login.
You can click on little Post icon to post feedback and review what is being posted by other insiders.
Click on Add new feedback button will open the New Feedback window where you may select between a suggestion or a problem. Select category and other options provided below and post feedback.