Yes, it is allowed, as long as they are not being used to violate the Community Guidelines and not being used to evade a ban on another account. Note that you are only allowed to have one account on the Scratch Wiki unless it is a bot, as it is otherwise known as sockpuppeting.

Uses

These are some common uses for alternate accounts:

  • Testing
Main article: Test Accounts
To test Cloud Data or share tests for current projects as a user that is not the account who made it, users need a second account.
On the Scratch 1.4 site, test accounts were used to upload test projects and to see if they work well online. They are still used today, especially if Scratch 1.4 is used to make the projects, but not too much for this purpose.
  • Remixing
Main article: Remix
This kind of account is used explicitly for sharing remix projects, such as contest entries or projects which help others. Some people use test accounts to share remixes and other types of project.
  • Collaboration (group)
Main article: Collaboration
This kind of account is to share projects made from collaborations and companies. These accounts are used to "brand" the project with the name of the collaboration. Many of these accounts are controlled by the entire team, not by the leader, but this is strongly discouraged by the Scratch Team.[1] However, you can still have collaboration projects, studios, and other things on Scratch by making an account for collaboration, but not tell the other person the password. Then you can start a collaboration project on your profile. The person would then remix your project and you would remix theirs. This could carry on forever. When you agree with the version, the person who created the collaboration account can upload the polished (finished) version of the project.
Users also use alternative accounts for remixing collaboration projects to improve them.
  • Helping projects
Main article: Tutorial Projects
When helping another user with scripting or another concept of Scratch, it is often beneficial to upload a project for them to directly view the concept first-hand. These informative, helping projects are often shared from test accounts.
  • Low-quality projects
Another use of test accounts is to share projects that would be "embarrassing" to have on one's main account. This could be things like basic projects which are not of the quality a user might want on their main account.
  • Roleplay
Main article: Scratch Trends#Roleplaying accounts
Roleplaying can be used by a test account to keep cluttered comments, projects, and/or studios off of the user's main account. Sometimes a user will assume the role of a character and pretend to be him/her/it with other users playing along.
  • Aesthetic Sets
Aesthetic sets are another use of a side account. Scratchers will upload photos of a certain theme and make five projects with different photos or simple artwork as the thumbnail (and entire project.) These projects can be favorited by other users so they appear on their profile. Users will make a separate account for this so they don't "clog" their main with just photos.

References

  1. https://scratch.mit.edu/discuss/topic/183361/