When I hit Return after entering a number in a cell, the cursor automatically drops down to the next row under the cell. How can I disable that, so it stays on the cell I entered and I can move on my own to wherever I want to make my next entry? I use the num pad when entering into a spreadsheet and it is habitual to hit "enter" after inputting numbers into a cell, then arrowing to wherever I need to go next (often to the next column rather than the next row.) There was a way to disable the automatic movement in Excel, but I've not been able to find a way to disable in Numbers.
Not exactly what you've asked for, but try pressing Command+Return while the cell is still in edit mode, instead of just Return. This should keep the same cell selected.
Edit after OP clarification:
There is no option to disable cursor movement on Enter in the latest version of Numbers. It used to be there in earlier versions (pre 3.0, I believe).