SAP TM ERP Document Flow Navigation Through Fiori
SAP Transportation Management (TM) allow users to navigate form the ERP documents direct to the Freights Documents.
In the previous version of SAP TM, the navigation through the Freight Documents was in NWBC, which was the Front End for the Key User, now with S/4HANA Key User use the Fiori Launchpad.
Through the navigation from the ERP documents Key Users can see many data and follow up the process of Planning and execution for the Sales Order, Delivery, etc.
For example, from a Sales Order user goes to TM Status Tab and see a lot of information from the Freight Documents.

TM Document Flow.

Every Use who has access to navigate through the TM Document flow jus clicks on the Freight Document, and it open a new session in the browser to visualize the Freight Document.
If you notice in the Browser once you open i.e. a Freight Unit the section is based on NWBC, this means you can still do any action if need in the Freight Unit but you’re not able to navigation through the Fiori Launchpad.

From a Key Users perspective this session of the Freight Unit is exclusive and can’t get back to the Fiori Launchpad
From a technical point of view if you want to allow the Key Users navigate to the Fiori Launchpad and not NWBC, you can add the User parameter WEBGUI_IS_IN_FLP = Y, in Transaction SU3 this will allow the Key Users open the Freights Documents from the ERP direct in the the Fiori Launchpad mode.

After adding this parameter, you can see the difference for the Fiori Launchpad mode.

Note: Login in the Fiori Launchpad might be request.
Refer to;
3577612 - How to navigate to the Fiori Launchpad to open TM documents from ERP document flow. - SAP ...
3199167 - TM: Create fully-qualified FLP-based document URLs - SAP for Me
2708480 - SAP TM embedded in S/4HANA - PFCG role concept - SAP for Me
Hope this help you!
Thank you and regards.
Rogerio Lima.