ArcGIS Pro 3.4 adds Attributes to the toolbox spec which adds extra options to script tools that were previously limited to default tools. The catch: these can't be added to Python Toolbox tools, at least not in any stable or documented way.
Please add support for Python Toolboxes. An "attributes" property on each tool that stores a list of attributes to set would align with how ATBX files store this info, something like:
class Tool:
def __init__(self):
"""Define the tool (tool name is the name of the class)."""
self.label = "Tool"
self.description = "My tool that edits the input data and costs credits."
self.attributes = ["input_data_change", "credits"]