To add a timesheet entry

To hide the Budget and Role Fields in the timesheet screen see topic on User Preferences in particular the section on the Screen Tab

Keyboard Shortcuts:

Press Tab to go from field to field, Shift + Tab takes you the other way.
Using F4 or Alt + will open the lookup without using the mouse.
If a field is highlighted, pressing your End key will put your cursor at the end of the line.
If you press Tab to get to the Add New Timesheet button, once it is highlighted you can just press your enter key to add a new timesheet.
You can also press Ctrl + to go straight to the Add New Timesheet button.
Click the Cancel button to exit without saving.