When you invoke the Hook window, it needs to identify the current item (document or object). If Hook cannot identify it, the status bar message will say
No linkable item found in
<App>. Learn more
<App> is the name of the app. For example, “No linkable item found in Mail.”
There are four likely explanations for this situation.
1. The foreground item has not been saved
It is impossible to link to (or from) a item until it is saved. Some applications (e.g. Notes.app, Bear, nvALT) save new items as soon as they’re created, but many applications (e.g. TextEdit, BBEdit, Photoshop) let you open a new window and start writing or modifying new items which don’t exist in the file system and cannot be hooked until they are saved.
Tip: Save new items before invoking Hook on them.
2. The message is a draft email, or the email app does not have automation
Hook normally identifies emails by their standard “Message-ID” , per Section 3.6.4 of RFC 2822.
Until an email message is sent, the message does not have an ID. Therefore it cannot be referenced.
If you happen to use the Spark email client by Readdle, as of 2019-12-05 it still does not support automation to get the name and ID of emails. Mail.app, MailMate and Airmail 3 and even Outlook do support automation.
Tip: Use an email app that supports automation, and make sure you are dealing with a message that has been sent.
3. No item is selected, open or loaded in the frontmost window
If the frontmost window has no object, or no object has been selected, then there is no item for Hook to get information about.
If you are in an app but have not opened an item, then there is no item for Hook to get information about.
If you have accessed a web page that has not yet loaded, it is not possible for apps (including Hook) to tell what the address or name of the web page is.
Tip: Ensure that the correct window is frontmost, and that the desired item is open or selected.
4. The Application is unsupported
Most macOS applications work with Hook but some require special support for their integration.
Tip: Learn more about integrating Hook with unsupported applications.
Ongoing and future developments
CogSci Apps, with the help of its savvy forum members, keep increasing the reach of Hook.