in appscript/main.gs [241:251]
function showProcessorPicker() {
let html = HtmlService.createTemplateFromFile('ProcessorPicker.html');
html.fileId = null;
html.fileName = null;
html.fileUrl = null;
html = html.evaluate();
html.setWidth(600)
.setHeight(425)
.setSandboxMode(HtmlService.SandboxMode.IFRAME);
SpreadsheetApp.getUi().showModalDialog(html, 'Process with Document AI');
}