Eclipse XSD editor

Which Eclipse package did you install? The XSD editor isn't included with all of them. If you click on "details" for any package, you can see the included features. The one you're looking for is org.eclipse.wst.xml_ui.feature.

Apparently the XSD editor wasn't included in my package (Eclipse IDE for Java Developers). I added it using:

Help > Install New Software...

Work with (enter your Eclipse version, here Photon):

Photon - http://download.eclipse.org/releases/photon

Filter by "XML" - as "XSD" wouldn't return the XSD editor (eventually untick "Hide items that are already installed" in case it's already installed):

Web, XML, Java EE and OSGi Enterprise Development

And then:

Eclipse XML Editors and Tools

Example with Photon: