I have a customer object as master and Document object as Detail which has a Status__c field. Since its a Master-Detail there can be multiple Documents to the custom object.
I want to maintain a field in the Custom Object(Master) which tells me if all the Documents Status is "Verified" or not. i.e. for example, I can have a checkbox field in Master obj, which will be true when all the documents(detail) have status as Verified.
You'll have to either write code, use a third-party application like DLRS, or (if applicable) combine several out-of-the-box customizations to achieve this result.
The hopeful situation is that your Status__c field is just a text field and can be filtered in a native Roll-up Summary Field. If so, you could solve this use case by creating two Roll-up Summaries from Document to Customer. One would be a COUNT() summary of all Documents, and the other would be a COUNT() summary that filtered based on the Status__c field.
Then, you'd add a formula field with the type Checkbox which simply compared the two Roll-up Summaries to obtain its value.
If that doesn't work for some reason, I'd recommend implementing the same pattern with DLRS rather than writing an Apex trigger or triggers from scratch.
