How can I append an arbitrary suffix to the target url, when using Target Servers?

[#1]

I have 2 proxies calling internally calling Proxy 1 to Proxy 2 using path chaining. First endpoint in Proxy 2 returns a message back to Proxy 1 for additional processing then it calls Proxy 2 again on a different endpoint.

Proxy 2 needs to use the same target, which was invoked in first call, but with a different endpoint (endpoint basepath is same, but path suffix is different).

I am setting context.setVariable('target.copy.pathsuffix', false); using a javascript in preflow of target endpoint. This worked when on first call on proxy 2 while invoking a Target. In Second call target target.url is blank so I am not able to set path preffix.

Can you please advise?

---

Here I have simplified:

My proxy uses Target Servers.

The TargetEndpoint looks like this:

<TargetEndpoint name="Sampleservice">
  <PreFlow name="PreFlow"> 
    <Request> 
      <Step>
        <Name>JS-AddPathSuffix</Name> 
      </Step> 
    </Request> 
  </PreFlow> 
  <HTTPTargetConnection> 
    <SSLInfo> 
      <Enabled>true</Enabled> 
    </SSLInfo> 
    <LoadBalancer> 
      <Server name="testserver"/> 
    </LoadBalancer> 
    <Path>/v1/sample</Path> 
  </HTTPTargetConnection> 
</TargetEndpoint>

This is the logic for AddPathSuffix.js :

context.setVariable('target.copy.pathsuffix', false);
var targeturl = context.getVariable('target.url');
context.setVariable('target.url', targeturl + '/contacts' );

I want it to call https://testserver.com/v1/sample/contacts but it is calling https://testserver.com/v1/sample .

How can I append an arbitrary suffix to the target url, when using Target Servers?