Go to https://stretch.parametricfab.com/ in a browser with WebGL 2. You can try the built-in bracket or open your own STL.

Choose X, Y, Z, a custom angle, or a direction from a model face. Set the start and end planes with the number inputs, the round handles, or the pick buttons.

Enter a positive number to stretch the section or a negative number to shrink it. Choose whether the start side, end side, or center stays fixed. Details inside the section stretch with it.

Export STL saves the preview. Apply stretch commits it so you can make another edit. Open the exported STL in your slicer, check it, and place it on the bed if needed.