How to load plugin after build in CKEditor5?

Question

Currently working on a project that require the CKEditor5 to show a custom button in certain scenarios. The button would have the function to interact with some information on the site.

The only way to include the custom button in the toolbar in CKEditor5 is to create the plugin and build it. However, it would not be able for us to edit the button function when using ClassicEditor.Create(...) . Is there a way to either create a custom button in toolbar without using plugin (maybe extraPlugins: [] would help?) or able to change custom button function in the process of creating CKEditor.