The available Keyboard Shortcuts used in Workbench are:
CTRL + M Search a menu item
CTRL + I Inserts a new object or a line on editable grids. Allows you to create Timesheets, Expense claims and etc.
CTRL + S Saves dialogs (popups) or forms
CTRL + B Navigates back to a previous screen if the Back button is presented
CTRL + > Navigates to the next timesheet
CTRL + < Navigates to the prev timesheet
CTRL + A Apply filter and focus on the first input element
CTRL + G Focuses on a grid line
CTRL + P Shows the Workbench report dialog if the Print button is presented
CTRL + 1 to 9 Navigates between tabs on a dialog (i.e. Companies, Jobs)
CTRL + up/down In some screens, allows navigation of some grids