tracking issue for correctly setting custom-variables

[lebensterben]

Currently many custom-variables (those defined via defcustom) are set via setq or setq-default. We should instead set them with custom-set-variables. The benefits are:

• It's only set when its defcustom form is evaluated. So in case we made a typo in the variable name, the symbol won't be created.
• It won't appear in customize-rogue

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Please let us know if this issue is still valid!

[bcc32]

I think we should re-open this issue. It is worth doing.