This is the place where you configure a sheet you would like to process. Everything that you configure here is saved and automatically restored by the add-on once you switch back to the sheet.
A source sheet is the sheet which is currently selected in the add-on. If you want to process a sheet in a spreadsheet, you have to switch to that sheet first. You need to tell the add-on explicitly which sheet you would like to process. The add-on will try to restore the entire configuration for that newly selected sheet if it was configured before.
This way, you can have a different sheet configuration for each sheet in a spreadsheet. By switching between sheets, the add-on will load different configurations.
Select a draft you would like to use as a template. The draft must contain at least one merge field. The add-on creates a copy of the draft for each row which is being processed, and replaces merge fields with data from a sheet.
TIP: Take a look at how to create your first merge draft.
Select a label which you would like to add to each created or sent draft. This is optional but strongly recommended. Once messages are labeled, you can easily filter them out in your Gmail folders.
Configuring A Sheet
There are a few things you have to always do every time you process a sheet: