You can place new items into the global navigation menu in several ways. In my earlier posting, I showed the case of using a Python script (add-external-tool-for-course.py at https://github.com/gqmaguirejr/Canvas-tools ) . However, there was a request for something with pictures - I have done this addition to another menu via an alternative method - in this case using custom Javascript inserted into the site. However, with all of the pictures, the document is a bit long, so I will provide a pointer to the example code (add_language_global_nav_item.js) and document (Better_language_support.docx) at https://github.com/gqmaguirejr/E-learning
The current code, simply adds the menu item as a small Canvas settings icon with the text below it showing the current locale, the URL used is just the URL of the university's main webpage.
Note that the context of want I am working on is a way to make it easy for our students to be able to toggle their UI language between Swedish and English and then later use this to also toggle which content is presented in a course page based on the currently set language.
If you are just interested in the Global Navigation menu and modifying it, see Sections 4 and 5 of the document.
For another example of adding semantics to an added menu item (in the course navigation menu) see Adding_URL_to_call_to_external_tool.docx at https://github.com/gqmaguirejr/E-learning ). In this example, you can see code that checks not only what sort of page the user is on but also checks whether the user is a teacher or not. So if you want to have a menu item only on certain types of pages and only make it available to a TA, this is straightforward to do with custom Javascript for a Canvas instance.
What I not done in the above is to do this for Microsoft Teams - as I don't use this tool, but given that it can be invoked by LTI - one could add URLs for it to the global or course navigation menus, just as adding it to a page. My assumption is that the integration via the RCE button is rather deep and also includes putting entries in the course calendar, etc.