Yes. A rest call via rest api explorer, and editing the JSON with the raw tab .

Here's an old discussion where someone was trying to set location.latitude and location.longitude in a table API PUT call:

TABLE API write options

At the end they state "this is not currently possible with the Table API."

If that is still the case, you could create your own inbound REST API call and set as many table records as needed with GlideRecord queries.

Yes, That what I did. the problem is that I only get the fields name and value and not the table. 

Unfortunately, dot walking does not work with setValue() , for example gr.setValue ('assigned_to.email', 'my@email.com') doesn't work even if you call updatewithreferences() in the end. 

To bypass that problem, I created a string that contains the script syntax, for example, it's generating these commands: gr.assigned_to.email= 'my@email.com'; and gr.updatewithreferences() and run it with evaluate script command. 

for reference fields you have to pass the SysID not the value if you are updating or inserting values through script.

Thank you, But I didn't ask how to update a reference field but how to update fields inside the reference record. 

FYI, it's not mandatory to pass the sysID of the reference, you can set the sysparm_input_display_value to true and pass the display value of the reference field.