In ArcMap, the Toggle Reference Scale tool was available via the Production Mapping extension as referenced here - Toggling reference scale for edited representations—ArcMap | Documentation
I've looked for similar functionality in ArcGIS Pro and "think" this may be what you're looking for - go to the Layer Properties of your layer in the Contents Pane, click the Display tab and under Scale there is a checkbox "Scale symbols when a reference scale is set" - is this what you're looking for? If not, please let me know what specifically you're looking for. Thank you!