Describes the cause and action for error messages.
Error Message(English)：
subtotal buttons missing excel
Where is the Subtotal Button in Excel 2007, 2010, 2013, 2016, 2019 ...
https://www.addintools.com/documents/excel/where-is-subtotal-button.html
Subtotals in Excel: how to insert, use and remove - Ablebits.com
https://www.ablebits.com/office-addins-blog/2016/08/11/subtotal-excel-insert-use-remove/
How to insert subtotals in ...
https://www.ablebits.com/office-addins-blog/2016/08/11/subtotal-excel-insert-use-remove/#insert-subt・・・
How to use subtotals in Excel
https://www.ablebits.com/office-addins-blog/2016/08/11/subtotal-excel-insert-use-remove/#use-subtota・・・
10+ tips for working with Excel's Subtotal feature - TechRepublic
https://www.techrepublic.com/blog/10-things/10-plus-tips-for-working-with-excels-subtotal-feature/
subtotal outline not working | PC Review
https://www.pcreview.co.uk/threads/subtotal-outline-not-working.3967087/
Excel 2016: Groups and Subtotals - GCFLearnFree - GCFGlobal
https://edu.gcfglobal.org/en/excel2016/groups-and-subtotals/1/
Show or hide subtotals and totals in a PivotTable - Office Support
https://support.office.com/en-us/article/show-or-hide-subtotals-and-totals-in-a-pivottable-fc4d8406-・・・
How to show or hide outline symbols in Excel? - ExtendOffice
https://www.extendoffice.com/documents/excel/1180-excel-show-or-hide-outline-symbols.html