I want to use CKEditor 5, insert image with URL dialog, instead of its default file upload dialog. how to do this in CKEditor 5 Classic?
There is, as far as I know, no such feature officially provided. There is, however, a tutorial provided in the documentation on how to write such a feature: https://ckeditor.com/docs/ckeditor5/latest/framework/guides/creating-simple-plugin.html
There is also a separate project on github for the same purpose, which appears to be a bit more stylish: https://github.com/khanhna/ckeditor5-image-via-url
Both approaches require to configure a modified build, and both appear to lack an important component: a button in the image's toolbar to edit that URL later on.
So, a more simple approach that does achieve practically the same is to just drag the images into the editor from some browser window.