There are 3 ways to do this. You can do it the same way you've been doing it, except there's a faster way than moving the nodes. Duplicate the letter, then switch to the Selection tool if not already using it. Grab one of the arrows. Hold Shift and Ctrl at the same time, then drag inwards.
However, that might not result in the same width of the outer line. If that's a problem, then instead of scaling, you can use Path Offsets, such as Path menu > Inset or Path menu > Outset. Or there's Path menu > Dynamic Offset which allows you to drag it to the right amount, rather than click Inset or Outset a few times. Info in the manual:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Paths-Editing.html#Paths-OffsetsOr depending on the particular font that you're using, the best solution might just be to add a stroke, and adjust the width of the stroke. To add a stroke, you can use Object menu > Fill and Stroke > Stroke Paint tab. Or you can hold Shift and click on some color in the palette. Either way, after that, go to Object menu > Fill and Stroke > Stroke Style tab > Width, to adjust the width of the stroke.
For the example you showed, the text isn't necessarily used at all to create the black outer border. They might have just drawn the area around it with the Pen tool. Or they might have converted the text to path, combined all the paths, then used Outset. Or they might have enlarged a duplicate of the text, and intersected it with a rectangle.
There's probably a tutorial or 2 or 3 for this, around somewhere. Let's see if I can find one..... Hhm, no I didn't find one, but I didn't use a search tool, I just looked through our collections. But you can try searching, and probably find one.
Or if you want to share an SVG file, I'll be glad to use it, to write steps for the best way, considering what you're working with and what you want to achieve. It's hard to give specifics when you only give us a general idea what you want.
