Widget Builder Widget - Shared?

I am planning out my first widget and it will be a slide banner for tops of the pages. On paper I have figured out how I will create the widget, however from what I remember from the demonstrations, I need to open the page, click the left layout tab and then pull the widget into the page that way.

However, I currently have one banner for each specific website (now 171 websites) and I place them on the design so they are on each page.

I have decided my work flow will be to place generic images in a slide-images folder for all to exchange - as well as have folders for each department, since they send images to me to crop and resize. I will simply upload them here.

But my question is - I’ve figured out the widget part - except would I have to apply this widget to every page within their website and when they wanted to exchange banner slides - they would have to do it to each page via the widget I created using the widget builder?

Example: I have a website called WCM. I want to create a slider using the Widget Builder I create in the system. Would I need to open my layout tab on every single page and snap in the widget > and > when I want to exchange slides > do this on every page in addition? Or is there a method by which this can be “shared” across one website - as I do for the existing sliding banner?