The Section/Elevation/Interior Elevation etc. windows contain content generated from the model. This adds to the size of the Project File.
The size of the model data is of course dependent upon the amount of model data to be generated based on what is visible per Layer Settings.
You can generate a Section with all Layers hidden. In that case there will be no model data generated in the Section and it will not add to the Project File size.
The Compress button is supposed to decrease the size of the Project File dramatically. I think it is a good idea to leave it ON.
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