You can get syntax highlighting and word-based completion in mdx files via a TextMate bundle support in WebStorm 2019.2.
To enable it:
- Download the sources of the vscode-mdx plugin
- In WebStorm, open Preferences/Settings | Editor | TextMate Bundles
- Click on the Add button and select the folder with the downloaded plugin
- Apply changes and close the settings dialog.
I would also like to let you know that we do not plan to implement MDX support in the upcoming WebStorm 2019.3 (because this release is going to be focused on improvements rather than new features). We will consider this feature for one of the releases in 2020. Thanks for understanding!