You can create an assistant administrator by assigning the access rights to them , for a client.

Follow the below roadmap on how to add an assistant administartor :
Roadmap: Hamburger menu -> Client/Trader Manager -> select a client to whom you want to assign rights for assistant administrator and click on View/Edit  -> Manage Assistant Administrator -> Click on Add Assistant Administrator -> Enter all the details and click on Save data & back button

You are provided a demo for how to add & view edit assistant administrator details.