How to set subfolder from s3 bucket as root folder in file manager

I’m using s3 bucket for file manager, i have different projects and for each of them i need to create their own folder for files and set it as root folder for file manager, how can i do that?

I did that on backend, but i want to know if i can set custom params to query, currently i do like that:
webix.attachEvent(‘onBeforeAjax’, (headers) => {
headers[‘Project-Id’] = projectId;
but i want to know if i can do something like that: