The File pull-down menu contains the following entries:

New (Ctrl+N).
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Creates a new document called untitled.xxx. Where "xxx" is the suffix 
for the specific editor. You can set the name of the new document in 
the document name text field.

Load (Ctrl+L).
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Pops up a file selection dialog to select the external file name for 
loading a document from file.

Append (Ctrl+A).
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The append of the diagram editors pops up a file selection dialog to
select the external file name for merging the current document with 
another one from a file. Diagrams that are appended, can be positioned 
at an arbitrary place in the drawing area by means of a paste box.

Tables can be appended either below or to the right of the current 
table. This is determined by an option menu in the append table file
selection dialog.

Append is an undoable command.
 
Save.
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Saves the document to an external file. If the document name is still 
"untitled.xxx" a file selection dialog pops up, like Save As. Otherwise
the document is immediately saved in the file "document-name.suffix" in
the project directory.
 
Save As (Ctrl+S).
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Pops up a file selection dialog to select or type in the file name to 
save the document to. After clicking OK, it acts the same as Save.
 
Save Selection As
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Pops up a file selection dialog to select or type in the file name to 
save the selected part of the document to. In diagram editors the selected
shapes and the corresponding part of the graph is saved to file. In table
editors the rows and columns that contain one or more selected cells are
saved.
 
Quit (Ctrl+Q).
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Quits the editor. If your current document is modified, it first asks you 
if you want to save the document.