One of the most powerful features of Excel is the formula and the ability to copy the formula easily across rows. But in a scenario where rows are filtered in other columns, the shortcut will not work -- this applies to both Excel desktop and Excel online.
Rows filter >> double click bottom left of formula cell
- will copy the value to all the rows below if all rows below are blank
- will stop copying when it reaches a row (filtered or unfiltered) that is not blank
Rows filter >> manual copy and paste the formula
- works, the filtered rows will be ignored, and the value will not be overwritten from the paste