How do I resize that big flower? Yes, I can edit it in Yellow Pencil. But that edits only one page. Is there any way while I’m creating a blog post to quickly adjust the header image size
Developing custom code for custom functionality is beyond the scope of support that we provide here.
If you are not a developer then you can consider hiring a developer to develop it for you. You can hire a developer from any freelance site. Shufflehound recommends the developer https://www.upwork.com/freelancers/~011652ffec8865c6d5