To keep Surfer from reverting to the default scale and limits, overlay map layers by adding a new layer to the existing map. You can do so by selecting the existing map and clicking Home | Add to Map | Layer. If the new overlay or map data exceeds the current limits and scale, you are asked if you want to adjust the limits and scale - simply click No. Dragging and dropping a layer into another map or using the Map Tools | Map Tools | Overlay Maps command will result in the map reverting to its default limits and scale.
The only exception is when you add a 3D surface layer. If adding a 3Dsurface layer to an existing limited map, the limits will expand to the data limits and the scale is reset to the default.
To add your vote to the request on the suggestion file to retain the limits and scale when overlaying maps, please email: firstname.lastname@example.org
Updated September 2, 2020