You can call a custom function like this example – it will set the status and then trigger the normal save function:
Add this to a HTML section in a tab:
<input type="button" value="Button text" onclick="your_custom_function_name();" />
function your_custom_function_name(){
setFieldValue("Status","The Status you want to set");
spjs.dffs.triggerSave();
}
Change the field name Status and the value you want to set.
Alexander