Here is what I do in such a case:
The Info Box always shows the state of the last selected element.
So, select all dimensions, then unselect a dimension that you know is not static (SHIFT-click), then again add it to the selection (another SHIFT-click). Since it was the last selected element, its settings are shown in the Info Box, including the Static Dimension checkbox being unchecked.
Simply check the static Dimension checkbox, and all Dimensions will be made static.
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