REST API call in OpenText TeamSite

Is there any way to call REST API in TeamSite? For example in .Net application we can use visual studio solution and call REST API via HTTPClient but working pattern in TeamSite is completely different. TeamSite has one admin portal where we can see files organized in tree structure for example index.aspx but there is no VS solution to write any code. It keeps everything in admin portal. The only way is using inline code approach as explained in Write Inline code

Is there any better way that TeamSite support for REST API call. Basically we need to call REST API which will return data in JSON format and set data in JavaScript variable. We need to use returned data for further processing for all pages

TeamSite version: 20.2.0.5