Because on the excel card you use a dynamic file, meaning it doesn’t exist at design time, you need to provide a template file in order to be able to use indicate or select any objects from inside it (tables, ranges, sheets) in order for you to be able to build your workflow, at design time.
So, because the WF is already build you don’t need that now and that’s why is not present in the project. But for example if you would like to add a write cell activity to write to the file “Vendor List-> Full Name” you wouldn’t be able to use indicate unless you provide a template to use it as a model for designing your wf.
So if you know that at run time an excel file will be created (for example you are downloading it from a mail) you need to provide a template to design the wf and the template needs to contain the exact structure that the dinamic file will have.
Hope it was clear