I am using Excel for Microsoft 365 MSO (Version 2111 Build 16.0.14701.20254) 64-bit
Back in the day (over 20 years ago) I was importing a lot of csv files with a lot of data in each. I was graphing this data and wanted a way to easily select all the data. There were thousands of lines sometimes. I remember finding a command I could add to the toolbar that selected all cells that were contiguous with the cell you selected. The icon looked like a circle in a square with arrows pointing to each corner of the square. I looked at customising the ribbon but can't see it. Does this still exist?