How to add icon command to debug toolbar in theia extension

I want to add some commands to theia/debug toolbar. I have seen vscode: add support for `debug/toolbar`, `debug/variables/context` menus contribution and `debugState` `when` clause context · Issue #11871 · eclipse-theia/theia · GitHub which says how to implement it through vscode plugin. but I want to directly add commands to the debug toolbar in my theia extension, where is the key point?