Preferences / User Parameters - defaults need to be duplicated

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Problem description

All settings are implemented by User Parameters - either via our custom `Pref` widgets or by manually reading and writing to user parameters. Furthermore, every time some User Parameter is used user must provide default value which must be duplicated across the codebase:


This leads to many inconsistencies, visible mostly in the preferences. Furthermore each change forces us to update potentially multiple places which are very hard to find and so can easily lead to inconsistencies for new users that do not have the default value specified.

### Full version info

```shell
0.22dev
```

### Subproject(s) affected?

None

### Anything else?

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct