create a dashlet in leads modules

What is your SuiteCRM version? Or are you still running SugarCRM?

What you ask is not possible to do.

You could achieve something similar with a bit more work, by adding to the Detail view a new field, maybe of type HTML or iFrame. Then you could reference an URL or some HTML code to show what you want.

You could make a custom entry-point to provide that content. See this thread for an example:

(see also other posts after that one).

That creates a graph in a Dashlet, but since it’s coming from a custom entry-point, you could add it in an iFrame in any other view.