Question node.js under PLESK - where can I edit the start command?

[mbulm1]

Hello All,
I would like to deploy a node.js app that also includes ES6 elements!
Since my highest-available node.js version is 12.4, I would like to add the following flag to the "restart app" call:
--experimental-modules
Where exactly do/can I do this?
Thanks in advance for your efforts.
Best regards
Markus