Office Open XML Template Macro-Enabled (XLTM) represents files that are generated by Microsoft Excel as Macro-enabled template files. XLTM files are similar to XLTX in structure other than that the later doesn't support creating template files with macros.
Learn more about this file format here
GroupDocs.Editor (in GroupDocs.Editor.dll) Version: 18.104.22.168
public static readonly SpreadsheetFormats Xltm
Public Shared ReadOnly Xltm As SpreadsheetFormats
static initonly SpreadsheetFormats Xltm
static val Xltm: SpreadsheetFormats