Enabling a plugin for a specific theme only

[Heliosurge (Dan DeMontmorency)]

In Customize goto Component. look through the components listed there. There will be a component installed with Air Theme giving you the preview.

In the Air theme it looks like your looking for Topic Thumbnails.

Topic List Thumbnails

Summary Topic List Thumbnails allows you to show topic thumbnails in topic list views. Preview Theme category - Discourse Meta Repository Link https://github.com/discourse/discourse-topic-thumbnails New to Discourse Themes? Beginner’s guide to using Discourse Themes Install this theme component Optimized images are generated for the lists, and different resolutions are made available for high-dpi displays. Images a…

This one is similar and has other features when combined with a plugin(be sure to verify plugin is still actively developed if you want to use Sidecar)…

Topic List Previews Theme Component

This is now a Theme Component but has the option to add a complementary plugin. [GitHub-Mark-32px] Repository: get the code here: https://github.com/paviliondev/discourse-tc-topic-list-previews Install guide: Install a theme or theme component This can be complemented with the ‘sidecar plugin’: https://github.com/paviliondev/discourse-topic-previews-sidecar to add the following features: ‘actions’ (bookmarking, linking and liking from Topic List) Thumbnail Picker in the Topic Meta Editor. …