Only asking this question because no one else appears to have done so. In GIMP, when using Transform > Scale, the option to keep the aspect ratio (hidden away in the primary toolbox rather than the Scaling window) is not a default. Is there any way to make "Keep Aspect Ratio" a default? Thanks
Yes. Select the Scale Tool in the tool box. In the Tool Options, select the Keep Aspect Ratio option.
Click Edit > Preferences > Tool Options > Save Tool Options Now
You can also have GIMP remember the Tool Options settings in the current state just before exiting the program, by checking the Save tool options on exit option. If you don't want this to happen make sure you uncheck that option! Unchecking it will ensure the tool options you saved will never change.
Alternatively, leave the Keep Aspect Ratio option unchecked, and instead hold down Shift as you click and drag one of the corner handles, and the aspect ratio will be constrained. This is how I usually use the tool.
For more information, check the documentation on the Scale Tool.