how to construct input json to call REST end point with dynamic value

Content

We have the following input json in request to call REST end point

 

{
  "schemas": ["urn:ietf:params:scim:api:messages:2.0:SearchRequest"],
  "attributes": ["actorName","timestamp","actorDisplayName","clientName","adminRefResourceName","adminRefResourceId","serviceName"],
  "filter": "eventId eq \"admin.group.add.member.success\" and adminResourceName eq \"epm_user_provisioning_group\" and timestamp gt \"2020-10-01T04:42:34Z\" and timestamp lt \"2020-10-06T04:42:34Z\" and adminRefResourceType eq \"User\" and  userName sw \"abc\" adminResourceType eq \"Group\"",
  "startIndex": 1,
  "count": 500
}

 

where timestamp and userName  in filter are dynamic which will be populated from other fields.

The difficulty is the how to get this json contructed at runtime?  I tried to create a new type matching request payload and variable.  Tried to change that and assign it to callToEndPoint body, but getting difficulty in including the dynamic values present in other variables. The above request payload was from postman where it has escape character for " , but here it is not working . Also as in our company, the developer tools was suppressed, its difficult to debug.