According to an announcement by Google Ads on June 29, 2021, when we hit late July (about a month from now), and you’re an advertiser, you will not be able to create any new brand match modifier (BMM) keywords with the +keyword notation.
This shouldn’t be much of a surprise, as Google Ads said this back when Google Ads first announced that it was expanding phrase match to include BMM traffic.
Advertisers will still be able t edit attributes of their BMM keyword, but if you edit keyword text, you will be forced to change the keyword to phrase match.