Let’s take a look at the next scenario. You need to create new group for users which will have the full control in the browser. But will limited for using specific folders, creating files with specific extensions etc. in SharePoint Designer.
In this case we need to use Contributor Settings (Contributor Mode)
First Step.
Create New Permissions Level (Site Settings > Permissions > Permission Levels)
Click "Add a Permission Level"
Second Step.
Create Group using Permission Level that you created in previous step (Site Settings > Permissions)
Click "New Group"
Third Step.
Open SharePoint Designer.
Go to "Site" menu > "Contributor Settings"
Setup "Site Manager" as default and delete others Groups.
Then Click "Add" new group
Give the name and choose site permissions level that you created in the first step. After that switching menu on the right chooses the settings that you need.
Click Ok
