Same for me and I'm on Windows Spire R11.  It was there 1 or 2 updates ago.

Hi Jeff,

Thank you for your questions.

Currently, this feature is available in The Welkin Suite for Windows only, and soon our developers will work on its implementation in TWS Nova.

I will let you know when Lightning Previewer will be available for you in The Welkin Suite for Mac.

In addition, you can see our plans for the nearest months in the Announcing the Big Spring Release of the Welkin Suite article. This is mostly related to the Windows version, however, the Mac version of TWS have almost the same way for development.

Regards,

Kate

Hi initdotd,

Thank you for your post.

The current implementation of the Lightning Previewer in The welkin Suite for Windows enables the feature for organizations related to a custom domain: you should enable a custom domain for your Organization on Salesforce and you should use it during the project creation in the IDE.

We will extend the abilities for the Lightning Previewer in future versions of The Welkin Suite, and you can see this in our plans in the mentioned above article.

Thank you,

Kate

Hi Kate,

Thanks for the info regarding Lightening Preview against custom domain.  I will follow that recommendation.

Thanks,

Jeff

(What I found on Windows)

After running several scenarios, it seems that not only do you need to use a custom domain (my domain), you also need to enable security tokens.  The only combination I found that worked was to:

1. Right click project and choose properties
2. Provide a "URL" using your my domain
3. Provide credentials included security token
4. Save all, including Solution and restart.
5. Upon restart, Lightening Preview seems to auto open when viewing .app in IDE

Hope this helps others,

Jeff

Hi Jeff,

Thank you for your post with the detailed steps to enable the Lightning Previewer for already created TWS projects.

We will describe this information more detailed in TWS documentation.

If you would have any other questions, please contact us. We will be happy to assist.

Regards,

Kate