Excel

Sort data in Excel safely, sort by multiple columns and custom orders, and fix sorting that is greyed out or puts numbers in the wrong order.

Add a drop-down list in Excel with Data Validation, make it update itself from a Table, build dependent lists, and fix a dropdown that stopped working.

Use VLOOKUP in Excel with exact match, understand why it only looks right, fix #N/A errors, and know when XLOOKUP or INDEX MATCH is the better choice.

Unhide columns in Excel, reveal column A when the normal method fails, and fix the cases where Unhide does nothing because they were never hidden.

Merge cells in Excel, see what merging breaks in sorting and pivots, and use Center Across Selection for the same look without the problems.

Remove duplicates in Excel, choose which columns define a match, find them safely first with UNIQUE or COUNTIF, and fix duplicates Excel cannot see.