Describes the cause and action for error messages.
Error Message(English)：
unable to group in excel 2016
Excel: Group rows automatically or manually, collapse and expand rows
https://www.ablebits.com/office-addins-blog/2017/12/28/excel-group-rows/
How to group rows in Excel
https://www.ablebits.com/office-addins-blog/2017/12/28/excel-group-rows/#group-rows-in-excel
How to collapse rows in Excel
https://www.ablebits.com/office-addins-blog/2017/12/28/excel-group-rows/#collapse-rows-in-excel
Excel grouping tips
https://www.ablebits.com/office-addins-blog/2017/12/28/excel-group-rows/#row-grouping-tips
Outline (group) data in a worksheet - Excel - Office Support - Office 365
https://support.office.com/en-ie/article/outline-group-data-in-a-worksheet-08ce98c4-0063-4d42-8ac7-8・・・
Problem Grouping Pivot Table Items ? Contextures Blog
https://contexturesblog.com/archives/2018/01/18/problem-grouping-pivot-table-items/
How to group rows and columns in Excel | OXEN Technology
https://oxen.tech/blog/grouping-excel/
Excel 2016: Groups and Subtotals - GCFLearnFree - GCFGlobal
https://edu.gcfglobal.org/en/excel2016/groups-and-subtotals/1/
How to Group Rows and Cells in Excel - and Outline them too
https://spreadsheeto.com/grouping-outlining/