Okay, I understand what you mean.
Normally, the point or set of vertices that are snapped with the mouse and shift key are released when you release the mouse.
There is a setting that allows you to keep these vertices snapped in space, but this is not the default mode.
If, by mistake, some vertices remain snapped in space, you can always select them, remove the "Fixed Points" mode and restart the simulation normally or with the shift key.

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