I am not sure. But I think may be you can mask part of the ITO before electrodeposition and the remove the mask for thickness measurement

But i have tried this many time by using cello tape and teflon tape.But it is not fruitful due to diffusion of carriers and no step form.

Application of lacquer./ photoresist before electrodeposition might help.

Mark with marker on your film before deposition and sonicate with acetone after deposition if your film is not react with your film......it may works for sharp edge.

You can try with PMMA dissolved in chloroform. Paint a line in the surface of your substrate before electroplating and remove it afterwards with acetone or chloroform. In case you don't have access to PMMA, any non-conductive coating/paint will work, even nail enamel (as long as it is not etched away by your electroplating bath).