HI @bwang-tecoustics,
When you have a session of AutoCAD open and you double-click a DST file in Windows Explorer, it should open the Sheet Set Manager. It will not open a single file. The manager, while it could be used to accommodate a single drawing with one or more layouts, it is most typically used to manage multiple (shared) drawing files and associated layouts.
So let's look at it this way, if you have a single drawing in a SheetSet that contains many layouts as part of the imported sheets, how would the manager know which layout you wanted open when you double-click the DST file?
Or if you had multiple drawings with one or more layouts in the set, again, the Sheet Set Manager has no way to identify which of those you want to open when you select the DST file.
Here is an AKN Article that might help you to more fully understand the Sheet Set Manager.
Please hit the Accept as Solution button if my post fully solves your issue or answers your question.
John Vellek
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