API REST as data source

Hi
I want to use Timetonic API REST as data source in Softr.
Timetonic is like Airtable.
It works well for read data but I have a trouble to write data.

The API doc says that the data to write must be in url parameters (not in the body)

fieldValues={field1ID:field1Value,field2ID:field2Value,}

When I enter this parameter in Softr, It is paste as a placeholder !!
I try to encode { and } like this

%7Bfield1ID: "Test"%7D

But it doesn’t work

"errorMsg": "Wrong format for parameter 'fieldValues'",

Do you know what i can try else ?

Nota : In postman it works with fieldValues={filed1ID: “Test”}