Quick update on this thread: Text Blaze is now available both as a Windows app and also as a macOS app. Both of them should work with the desktop version of Slack. You can get them from these links:
Windows: Text Blaze: Snippets and Templates for Windows
macOS: Text Blaze: Snippets and Templates for macOS
If you need help installing these apps, feel free to reply here. If you are looking for another specific integration with Slack, feel free to create a new topic in Feature Ideas - Text Blaze Community 