It would be nice if you also could provide the format of the datetime you provided in certain functions, such as formatdatetime and converttimezone. It supports a parameter format, but that's the format of the output. It would be nice if you could also specify the inputformat.
Because if you now input a date in the European format 'DD/MM/YYYY' those functions fail as they only support a certain ISO-standard. A lot of applications don't use this format and only have the format above, which makes converting them in Flow/Logic apps a pain or just plain wrong (aka 10/072018 is interpretted as 7th of October instead of 10th of July).