Thanks for getting back to me!
I checked and found that the data I have created in the beta version cannot be converted in the current official version (why not?).
In the meantime, I have re-uploaded the file with the official version custom item (.vroidcustomitem) that I have.
Please re-download the included custom item data and use it.
(I am sorry if it is rude or inappropriate to you, since I use the online translation site.)