This is a fantastic script - thank you! I have spent a good few days evaluating Foundry, since many people rave about how it is so much better than Roll20. But I have come back to Roll20 as, despite some functionality limitations (please stand up, Transmogrifier!) and bugs (I'm looking at you, UDL!), the ease of use is so much better - often thanks to these kind of API scripts (which I find easier to use than Foundry modules), and the ability to find a method of doing what you want to do via these forums. It is thanks to API scripters like Keith, Aaron and many others who keep many people, myself included, from moving away from Roll20. One suggestion for this script, assuming I am not the only one wanting it - if you could set a "destination colour" for the windows to become when they have been converted, then I could draw all my windows in a different colour, and they would automatically change colour when converted, so I could easily know which ones were still to be converted. Maybe as an optional parameter, so people who don't care can just ignore the functionality?