The Load Redline menu item allows to open a redline markup file.
The Load Redline 
menu item opens standard Open file dialog window. Redline markup file is a dxf file with a simple set of entities.
Loading a Redline file becomes possible after you've switched the application to the Redline mode.
Redline files are usually stored in a special folder which is created automatically. The files themselves receive the name consisting of the name of the basic file, the Redline was created on, and an addition $$Model.DXF.
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