You just have to change the MFD language from the hard button. Then reopen the app.
If you're doing from the website you have to change you webpage language on your browser.
My widget from appstudio doesn't change interface language when I change language from Ru to Eng or vice versa by Language Button.
The same situation is for appstudio web-interface.
There is a process to add new features. Can you please submit your request via the Feedback DL so we can be in contact? To submit, Go to XAS, click on the Help Link, click on the Feedback Link. Please include information about your customer base? How many users does this impact? Thanks!