Is there a way to move the view within a detail viewport a specific amount?

If I have a couple of floorplans that are offset by 100’, it would be nice to be able to go into a detail viewport and move it exactly 100’ so I can have drawings in the exact same position on two different layouts.

In AutoCAD, you can type it ‘-p’ and choose and amount to move. Is there anything similar in Rhino? If not, I can just draw an index line at a set point on the floor plan (like a corner) and use that to position them.

Yes, it can be done. First make sure that the detail is the active viewport. If it is not, double-click inside the detail. Turn on (click) Properties Panel and display its Viewport Property page (click Viewport Property page icon - it looks like a camera). Unlock the detail (if it is locked) and set its scale relative to the model space. Double-click on the layout outside the detail to make layout the active viewport. Select the viewport and turn on its control points (press F10 key). Select all control points of this detail. Turn on Gumball. Use the Gumball to move the control points (probably by 100 units). Lock the detail. You probably will move the entire detail in opposite direction.