Why is it important: This tab contains lots tools which are essentials when we are creating applications to use with Microsoft Office programs. For example to insert From Controls and ActiveX Controls while creating a macro.
How to enable Developer Tab in Excel 2007
Step 1: Open a new excel and click on Excel Options.
Step 2: Popular menu – Show Developer tab in the Ribbon and click the Tick mark to enable Developer tab and then click OK.
Once enabled it appears along with the top row commands of other Excel Ribbon items.
Check out:How to enable Developer Tab in Excel 2010