If your Ruby project includes a gem like Spreewald Show archive.org snapshot that comes with some external step definition, RubyMine does not know about them by default and will highlight the step as an undefined reference:

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

To link these external step definitions to RubyMine, add the corresponding gems to your RubyMine-Settings:

• Go to Settings (ctrl + alt + s)
• Go to Languages and Frameworks
• Go to Cucumber
• There, add your gem (e.g "spreewald") via the little "+" from the bar on the right .

You might have to restart RubyMine to see the expected result.

Now, RubyMine no longer complains about undefined step definitions and allows you to dig into the definition via ctrl + b or ctrl + click.