Calc: Warn if cells of a row have the same values?

[flatpakuser]

Many scenarios

Phone number copy-pasting, unique IDs…

In many cases you could want to be warned, for example with the cell colored in yellow, if a cell has the same content as another one in the same column.

Is this possible already?

[sokol92]

The simplest method is conditional formatting of a range of cells. Condition: is duplicate.