Given you have two documents in your file explorer a and b
And a is open in the editor
And a contains the text Example contents
And the users cursor is after the last e in example
When the user drags and drops the b document into the editor
Then the contents of a equals Example[[b]] contents
An additional variation could exist for tags, where you drag a tag from the tag pane into the editor say #tag and it drops the very same value into the cursor location- in this example #tag