@zoltanleo
Thank you for your feedback and suggestions. I wanted you to know I considered each of those items during the development and decided not to include them specifically for a few reasons.
Regarding closing the dialog when pressing save, I omitted this because there might arise certain situations where you would want to export the same icon at several sizes, such as 96, 64, 48, 32, and 24px. Rather than force the user to continually reopen the dialog 5 times to do this, they can keep the dialog open and just change the size and press save. When you are done you can simply press `escape` on your keyboard to close the dialog.
Regarding standard icon sizes I think it's easy for someone to type 32 than it would be to click a combo box, find the item they want, then click the item. Also it would complicate things to have BOTH a list you can pick from in addition to a custom size field for instances where the size you wanted is not in the list.
Finally, regarding automatically naming the icon based on the material design icon name, I imagined many situations where the programmer might want to use a particular naming convention or a standard prefix or suffix in their exported PNG names. Rather than replacing the name each time a new icon is opened I thought it made more sense to preserve the name and allow the programmer or designer to alter the part of the name to fit their naming standards.
Of course I am open to making these changes based on a concensus.