I'm using Aptana Studio 3 on Mac High Sierra. I would like to configure a Rails server for my existing Ruby project. I have already imported the Ruby project into my workspace. However, when adding a new server, the drop down list is empty ...
Not sure what else I need to do to add a server configuration. Help is appreciated.

The issue comes from Aptana Studio cannot recognize your project is a Rails project.
Right click on your project in left panel, choose
Propertiesthen chooseProject Natureson the left side and checkRailson the right side,Apply and close. See my screenshotNow, you will see your project in the Project dropdown
Anyway, I highly recommend you to use another IDE because Aptana seems to be out-dated. Its last release is more than 1 year ago. Especially for Rails, its support seem to be stopped at Rails 3 because its start script still lookup
railsscript inscriptfolder instead ofbinfolder (so, you may also need to copy it frombintoscriptto be able to start the rails web server)