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->Select Special
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