After the September 2017 update, simulation users found that the "suppress all but selected" command was no more. This came as a bit of a surprise, but the trade off was getting the powerful new simplification workspace ---the history based nature of it is why the option went away (for now). The good news is that there are still ways to get similar outcomes; check out this QUICK TIP to see how.
To learn more about "remove rigid body modes" and how you should use it, see here: http://help.autodesk.com/view/fusion360/ENU/?guid=GUID-E34DCC0E-666C-429D-BBB6-BEFE40A7AE0C
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