Introduced in CrossClave v9.0, users can now mention files in the chat tab that have been uploaded to the channel the space resides in. This is done by selecting the paperclip icon below the chat field.
This will bring up a list of the files that have been uploaded to a space. Selecting a file from the list will append it to a message you enter into the field. Other users can then open the file or view the file in the files tab.