Hi Valerie,
Contacts Associated View is only applicable for contacts whose source journey field equals to current customer journey.
For example, run a workflow after contact submits form. In the workflow, set the source journey field to a specific journey record.
(For Lead entity, the source journey field will be automatically populated if the lead is created by Create a lead tile.)
Actually, it could be said that there is no direct relationship between Customer Journey and Contact, and Segment could be regarded as an intermediate entity connecting two entities.
Customer Journey <-> Segment <-> Contact.
Therefore, even though we can't see which contacts are involved in customer journey in form, but we can still get involved segments in General -> Segments used.
However, in the General tab, only leads subgrid is the real associated view(source journey), while records inside Segments used and Marketing emails used subgrids are retrieved by a special action called
"msdyncrm_EntityDependenciesRetrieve".(In other word, Segment and Marketing email aren't directly associated with Customer Journey too.)
Below is sample code to retrieve all associated segments of a specific customer journey.
queryRelatedEntities("e43540ce-18ec-ea11-a815-000d3aa08990","msdyncrm_segment");
function queryRelatedEntities(mainEntityId, relatedEntityName) {
var serverURL = Xrm.Page.context.getClientUrl();
var data = {
EntityDependenciesRequest: '{"EntityId": "' mainEntityId '",'
'"page": 1,'
'"IsBidirectionalRetrieval": true,'
'"TargetEntityTypeFilter": "' relatedEntityName '",'
'"TargetEntityLiveFilter": false'
'}'
};
var req = new XMLHttpRequest();
req.open("POST", serverURL "/api/data/v9.0/msdyncrm_EntityDependenciesRetrieve", true);
req.setRequestHeader("Accept", "application/json");
req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
req.setRequestHeader("OData-MaxVersion", "4.0");
req.setRequestHeader("OData-Version", "4.0");
req.onreadystatechange = function () {
if (this.readyState == 4 /* complete */) {
req.onreadystatechange = null;
if (this.status == 200) {
var result = JSON.parse(this.response);
var relatedRecords = JSON.parse((result.EntityDependenciesResponse)).Dependencies;
console.log(relatedRecords);
} else {
var error = JSON.parse(this.response).error;
alert(error.message);
}
}
};
req.send(JSON.stringify(data));
}

Finally, in summary, to see all engaged contacts of customer journey in the customer journey form, you need to insert a HTML web resource:
1. Call the action to get related segment name.
2. Use the retrieved segment name to get members of the segment with segment API:
https://docs.microsoft.com/en-us/dynamics365/marketing/developer/extend-segments#addremove-contacts-to-static-segments

3. Render result in a table.
Regards,
Clofly