I’m curious why the formula =ROW(PARENTCELL()) would be returning an error. If this worked, it could be used to do some interesting things. Currently, I’m trying to use the formula =ROW()-ROW(PARENTCELL()) so that I can calculate the current sibling number for automated outline numbering.

In the Construction Schedule template, I’ve used absolute references in place of ROW(PARENTCELL()), but if ROW(PARENTCELL()) worked, there would be no need to edit the formula for each set of sub tasks.

Thanks for the fix in the latest upgrade. The formula =PARENTCELL()&"."&(ROW()-ROW(PARENTCELL())) now works well for projects with just one level of sub tasks. And, if you don’t mind having WBS numbering skipped (going from 2.2 to 2.5, skipping 2.3 and 2.4), it also works for any number of indent levels. See the animated gif below as an example of indenting when the WBS column uses this formula:

Technically, when indenting Task 3 & 4 (making them 2.2.1 and 2.2.2), the WBS for Task 5 should change to 2.3. However, that would require a more complicated formula, as discussed in the following thread about WBS numbering:

For practical purposes, as long as you don’t mind skipping some of the WBS numbers, the ROW(PARENTCELL()) fix is now a useful way to implement some automated WBS numbering.

Filter: Filtering still works when using this formula.

Sort: Sort doesn’t work with this technique. Using manual WBS numbering and sorting by the WBS column is a way to sort rows instead of using Insert/Cut/CopyPaste to move tasks around. I still wish that there was an easy drag and drop method for moving rows instead of using Sort to move rows.