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Your LimeSurvey version:  Version 6.5.12+240611
Own server or LimeSurvey hosting: Research center (internal company) server
Survey theme/template: 
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Hi everybody,

we are planning to delegate the conduction of the survey to a panel provider. Required redirects have been implemented via panel integration tab etc. However, they now requested that we edit the welcome page and add another option/checkmark box with "No I do not agree". (see screenshot below) This is were I am stuck. Inside the user interface I can't find any function/field to edit the welcome page (beyond the text elements and the display of the privacy of policy). If anybody knows how to add this option, it would be highly appreciated. Thanks!

and add another option/checkmark box with "No I do not agree". 

And if the participant clicks it, what happens?
Is there a redirect to catch these respondents?
In this case you shouldn't show this "welcome page" but create a first page with a list(radio) similar to the welcome page - and use a quota to screen out and redirect these people.

In my opinion the easiest solution.

Joffm