I find that overriding the views is more intuitive for me whenever I have to customize something. https://guides.solidus.io/developers/customizations/customizing-admin.html

For example, if you want to customize backend/app/views/spree/admin/orders/index.html.erb , simply create a new file at

app/views/spree/admin/orders/index.html.erb

and copy the original contents into it. Make any desired changes to the newly copied file. Solidus will pick up the modified version of the file in your repository, and display the changes in the backend.