The whole process is OAuth, so to have some sort of function to either edit an existing token or generate a new token with additional scopes and NOT list all the other scopes the the token will have will be breaking the OAuth specification. While technically it may be possible, in my opinion there is not much justification for such a change when the vast majority have no issue with the current auth process.
That’s your choice, it just means that you wont be able to voice your use cases/needs/ideas in the place where it matters. It’s not “another account” though, as UserVoice uses your Twitch account.
While a suggestions section on this forum may be suitable in some situations, it does not provide the same flexibility that is needed and used by UserVoice, such as easily ordering feature requests to the relevant team, or access control to certain suggestion areas for users under NDA needing access to closed beta areas where they can make suggestions involving products not yet public. Such access control would be more complicated on places like these forums where user accounts are not always tied to a Twitch account.