Office-js - set icon to mailbox.item

Question

Is there way to set/change Mailbox.Item (https://learn.microsoft.com/en-us/javascript/api/outlook/office.mailbox?view=outlook-js-1.9#item) icon or anyhow mark Mailbox.Item from Office.Context so it is clearly visible from the overview?

I have searched the internet and found solutions that do not include Office-js at all. Maybe some workaround with setting Messageclass via EWS call and creating FormRegion, but I need it to be done via the Office-js web add-in.

This is the best lead I found Can i add custom icon to "outlook" item?

Answer 1

If you have access to the Graph api, you can add an extended property. You can only see this icon in an Outlook installed on Windows. Code in js:

const data = {
    singleValueExtendedProperties: [
        id: 'Integer 0x1080',
        value: '265' // or another number
    ]
};

request.patch(`/me/messages/${messageId}`, data);