I have installed Scala IDE plugins from Eclipse Marketplace but there is no option to create Scala project.
NOTE:
I am using spring-tool-suite-3.6.2.RELEASE-e4.4.1 Installed Scala IDE for Eclipse & Scala Worksheet since JDT Weaving is already installed in STS. Scala version: 2.11.2
Create a regular project then when you right click on it in the package explorer there should be a Scala sub menu and you can "add Scala nature". Now STS knows it's a Scala project.