There is currently no way to use tokens when specifying the directory where inline files/images (i.e. those uploaded through CKE in a textarea field) are stored. There is some discussion about this in another recent forum post.
It probably would not be hard to enable global and site tokens in the "Upload directory" configuration field for the text editor. On another post, someone was asking about using node tokens - that's harder, since CKE and textarea fields can be used in a number of different contexts (e.g. in long text fields possibly attached to taxonomy terms, user entities, and even in Custom Blocks), and (AFAIK) the Text Editors are "context agnostic".
If you want to ask for this feature (i.e. global and site tokens) you may want to open an issue in the Backdrop issue queue.