The Open button activates the standard Open dialog box.
Quick Access Panel: 
Ribbon: File -> Open
Menu: File -> Open
Hotkey: Ctrl+O
Please, specify the path to the file in the dialog box. It is possible to preview the drawing - check the option Preview active under the area of preview, which is in the right part of the window. The dialog box Open allows to open several files simultaneously with the help of holding the keys Ctrl and Shift pressed.
The opened file is automatically added to the list of Last files.
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