Some Boolean Attributes for Operators does not have Default Value

[AnzhiZhang]

What happened?

Some boolean attributes for operators do not have default values, so they appear as neutral checkboxes and confuse users.

See also: #4006 (comment)

How to reproduce?

Create an operator that does not have default values for boolean attributes. For example, Filled Area Plot and Dumbbell Plot.

In contrast, Bubble Chart has default values.

Version

1.1.0-incubating (Pre-release/Master)

Commit Hash (Optional)

No response

What browsers are you seeing the problem on?

No response

Relevant log output

[AnzhiZhang]

This bug can be a good practice for initial contributors. The solution is already available, and it will help them become familiar with the codebase and practice fixing it.