When opening an activity designer from RPA designer, the option to ADD new actions or DELETE some actions is not available. When using UFT only the option is available.
This is by design. In RPA mode, UFT is locked from allowing users to add new actions or delete the last action.
See “Edit an RPA activity using Activity Designer” section in https://docs.microfocus.com/itom/Robotic_Process_Automation:2021.02/AdvancedEdit. It says, “The current RPA activity will be in read-only mode as its steps and properties cannot be edited while the RPA Activity Designer session is open”.