Your first question regarding the Enlarger tool, does it work across multiple layers? Yes.
I tested this with a three-layer graph. Just make sure that Layer one is active when you use the Enlarger tool. Also, make sure that you have the other layers not only linked to Layer one, but also make sure you open the Link Axes Scales dialog box and link the appropriate X and/or Y axis One to One.

When graphs axes are resized to a smaller size, the data continues beyond the edges of the axes. Depending on the graph template that was used to create the original graph, [x] Clip Data to Frame may be turned on or off. In your case you want to make sure Clip Data to Frame is enabled on all layers. You access this property by first setting the appropriate layer active and then selecting from the Origin Menu Bar, Format: Layer. You would then check [x] Clip Data to Frame. You need to do this for all layers.

When you use the Enlarger tool, you are selecting the region of interest and basically telling the program where to set the start and end points of the x and/or y axes. You can do this from LabTalk using the Layer.Axis properties. Below is the format of this property. You can access the full set of property variables through the on-line LabTalk help using the Index keyword: Axis: Layer.Axis

The axis object is a sub-object of the layer object.

[winName!]Layer[n].axis.property=

WinName! Is optional. If winName! Is not specified, an axis in the active graph window is affected.
n is the layer number. If n is not specified, the active layer is used.

Axis is the axis specification: X is the bottom X axis, X2 is the top X axis, Y is the left Y axis, Y2 is the right Y axis, Z is the front Z axis, and Z2 is the back Z axis.

You state you want to rescale only the X-axis. The script below will act upon the dataset plot that is in Graph1, Layer 1. It will set the bottom x-axis from -10 to 10. Any other layers that are in the same graph window that are linked one to one to Layer 1 will also rescale. Again, make sure all the appropriate layers are linked properly.

GRAPH1!LAYER1.X.FROM=-10;

GRAPH1!LAYER1.X.to=10;