I understand your frustration with this issue. By default, when you press the "Enter" key in a text box in Excel, it will simply move the cursor to the next cell. However, there is a simple workaround to allow you to add line breaks within a text box.

1. Double-click on the text box to activate it.
2. Click where you want to insert a line break.
3. Hold down the "Alt" key on your keyboard.
4. While holding down the "Alt" key, press the "Enter" key on your keyboard.

This will insert a line break within the text box. You can repeat this process to add additional line breaks as needed.

Alternatively, you can also use the "Wrap Text" feature to automatically wrap text within a text box. To do this:

1. Double-click on the text box to activate it.
2. Click on the "Format" tab in the ribbon at the top of the screen.
3. Click on the "Wrap Text" button in the "Text Box Styles" group.
4. Your text will now automatically wrap within the text box as you type.

I hope this helps you with your issue.