presently the embed plugin allows files to be added inline into textbox fields and no way exists to easily and quickly link to existing elgg entities inline - beyond navigating to the entity and copy/pasting the url into the textbox.
i am envisioning a shortcut interface device to make adding links to existing entities quick and easy..
e.g. a button/link appears near to full size textboxes marked 'add link to' or similar. when that link is hovered over or clicked, a pop-up box appears that allows fast navigation of entities and when one is clicked a link is inserted into the textbox at the current/last position of the cursor.