To be able to edit Content Templates with a page builder such as WP Bakery it is first necessary to enable the legacy Views UI and specify that the template should be edited with the page builder (in Toolset > Settings), otherwise JS errors may arise.
When then editing a CT with WP Bakery, the WP Bakery UI buttons (e.g. to add elements to the template) appear inert, and clicking them has no effect.
A patch is available until the fix is included in a plugin update. Download and unzip the file backend.phtml from here. This file is included in the common code that ships with all Toolset plugins, and the one actually used on your site could come from any active Toolset plugin, and so you will need to replace the same file for all of your active Toolset plugins, in the sub-folder vendor/toolset/toolset-common/user-editors/editor/screen/visual-composer/ It may be necessary to clear the browser cache for the patch to work.