Formula or Rule for: "If Cell is Empty, Hide Row"

"Delete Categories" will return you to a normal view. Returning to categories you will have to reset your Category preferences. Probably not what you were looking for, but I'm not aware of another way.

Sorting on a column with zeros or blanks is a great way to group rows to be hidden.

It's possible to address both your needs by forgetting about Categories and creating your own custom summary tables by using formulas. There are many discussions here on doing that. Look for "breakout table" or "summary table".

Jerry

This is not done with formulas, it is done with filters. Open up the Reorganize window and look at the center section. You want a filter that says "show rows where column 'on order' is not blank".

This will work if the cell will actually be blank, nothing in it at all: not a null string created by a formula, no check box, no spaces, nothing. If it is something other than blank, you can still use the same basic idea but you'll have to use a different condition.

Adding to what Badunit says...

To return to the full view, click to uncheck the "Show rows..." box in the Reorganize dialogue.

Regards,
Barry