RenderHogs is an After Effects plugin from David Jacobson that lets you disable unnecessary layers and effects until render time. It also includes tools for maintaining responsiveness in heavy comps.
The plugin is compatible with a broad range of After Effects releases, from CS6 through CC, CC 2014, CC 2015, CC 2015.3, CC 2017, CC 2018, CC 2019 and After Effects 2020. The current version is 1.13, released on May 14, 2021, which added support for installation through the aescripts + aeplugins manager app.
First released in January 2015, RenderHogs has received updates addressing licensing and a fix to the 'Toggle & Render' button along the way. It's listed as free in this catalog, and a demo video is available. For current licensing and version details, see the developer's page on aescripts.