Edit . you can get all custom entities for the current user with the query
{
"entityType": "[entitytype]",
"ownerId": "[profileId]",
"context": {
"pagination": {
"rowsPerPage": 50,
"pageNumber": 1
},
"searchCriteria": {
// other search criteria here
},
"sortCriteria": {
"createdAt": 1
}
}
}