Is it possible to use third-party UI libraries like Material UI or Kendo UI within Apps Script for Gmail add-ons?

Question

We are developing a Gmail add-on and are currently using the built-in Card Services UI controls. However, these controls are limited and do not offer the level of customization we need.

We are looking for a way to incorporate more advanced UI features and customization. Specifically:

• Is it possible to integrate third-party UI libraries like Material UI or Kendo UI into a Gmail add-on built with Apps Script?
• If so, which libraries are suitable for this purpose, and where can we find references or documentation for integrating them?
• Additionally, if there are ways to extend the built-in Card Services UI controls for better customization, we would appreciate any references or examples.

Any insights or resources would be greatly appreciated!

Answer 1

No. Currently, Google workspace addons(not editor addons) use Card service to extend user interfaces, which do not support direct html/js libraries. However, if sidebar/modal dialogs are supported by the hosting app(eg: Google sheets), then Html service can be used to support these libraries even in workspace addons¹. But Gmail addon doesn't support sidebar or modal dialogs and therefore it is not currently possible to extend these user interfaces and the customization is limited to Card service functionality.