Craft Edge

Any way to adjust the scale of an image by scale?
1:20th scale to 1:1 scale without having to drag the image forever?

I hope I have understood your question correctly.

You can resize an image in the "position and size" panel on the right hand side menu, select the crossed arrow icons, and fill in the size you want.

If working in inches gives you too much or too little sizing try changing your unit of measure to mm or cm by opening the view menu in the top bar and selecting ruler units.

Here is a little cheat sheet showing the effects of clicking on the size changes in increments. I hope this helps. I use ecal2 and you don't say which scal you use but I think they all do it the same.