The following shortcuts can be used on the DocumentItems tab:
 

CTRL-A for Edit->Select All

CTRL-B for Edit->Add Blank Line

CTRL-C for Edit->Copy

CTRL-D for Edit->Delete Line

CTRL-E for Edit->Insert Paste

CTRL-F for Edit->Find

CTRL-G for Edit->Convert to Group

CTRL-H for Edit->Insert Heading

CTRL-I for Edit->Insert Blank Line

CTRL-J for {not assigned}                  

CTRL-K for Edit->Clear Line

CTRL-L for Product->Lookup

CTRL-M for Edit->Insert Comment

CTRL-N for File->New

CTRL-O for File->Open

CTRL-P for File->Print/E-Mail/Deliver

CTRL-Q for {not assigned}                              

CTRL-R for Edit->Line Attributes

CTRL-S for File->Save

CTRL-T for Edit->Add Subtotal

CTRL-U for Tools->Update Item Cost in Vendor Database

CTRL-V for Edit->Paste

CTRL-W for File->Close Document

CTRL-X for Edit->Cut

CTRL-Y for Edit->ReDo

CTRL-Z for Edit->Undo