The Tmetric start/stop timer buttons in for example GitLab are an awesome feature! But having them in the GitLab kanban board too would be even greater.
This integration won't get on our backlog in the near future.
BUT, you can help us add it by contributing to our browser extension. It's open sourced on GitHub - https://github.com/DevartSoftware/tmetric-plugins
Integrations folder lists all integrations we have. You can make one by example.
If you are willing to contribute, we'll gladly provide support and incorporate your code to our repository.