You can try the following, edit the file lib/core/db.js.
Line 76 looks like:
if (ast.type == 'insert' && ast.returning && this.client.config.client == 'postgres') {
Change it to:
if (ast.type == 'insert' && ast.returning) {
In you server connect action json file find the options for the insert step:
"options": {
"connection": "Target",
"sql": {
"type": "insert",
"values": [
{
Add an extra property to it:
"options": {
"connection": "Target",
"sql": {
"type": "insert",
"returning": "AppointmentID",
"values": [
{
Check if it now returns the id.