Guidelines for zero-border tables
Keep an invisible-border table easy to edit without adding an authoring outline to saved HTML. Guidelines are a Design presentation aid.
The table structure and its authored border styles remain part of the document.

Use it in your application
Enable guidelines for layout tables whose borders are zero. Configure the guideline style through the supported safe outline setting.
Inspect the exported HTML when a table must remain borderless. Guidelines are not the same as table border properties.
Use the table dialog or table authoring service to change actual cell or table styling.
editor.Options.ShowZeroBorderGuideline = true;
editor.Options.ZeroBorderTableGuidelineCss = "border: 1px dashed #64748b";
string savedHtml = await editor.GetBodyHtmlAsync();