OMG, I never actually checked before, and no, it looks like it can't be! This is ridiculous! The Quick Text Help Docs specifically don't mention chatter, and there is no little Quick Text Icon in the Post window, where there is in the Email compose window in the Case Feed. Also the handy ctrl+. (that is hold down control whilst pressing the period or full stop key), does not activate anything in Post, where it does in Email.
And No, Macros won't help either. You can't choose the Post button or the Share an Update in the Macro editor.
The convoluted way to work around it, is to:
- Create text field named Status Update
- Created a Quick Action with just the Status Update on the Layout
- Add a Related Record Component to the Case Page, and ensure it is ALWAYS VISIBLE (Macros only work on visible Quick Actions).
- Create a Macro, selecting the Related Record Component, then the Status Update field.
- Enter the Quick Text in the Status Update Field choosing Replace Existing Text
- Create a Process Builder - on field change of Status Update and add a Chatter Post to the record with the contents of the Chatter Post and then clear the Status Update field. Bonus, add a StatusUpdate topic to the Post so you can quickly get to a feed of all Status Updates
(Note: You could just do Feed Tracking on Status Update field but it would a) not clear the field value, b) show the previous and current post, and c) not allow you to add a topic).
But the whole idea is HORRIBLE because you would have to create a Macro for each and every Quick Text, which defeats the purpose of Quick Text, which is meant to be user editable.
What a completely horrible and ludicrous situation. Oh, and of course there is an idea for it. Note that the first post on the Idea says to copy the Quick Text and paste it into Chatter. Well again that defeats the purpose of Quick Text as you can't use Merge Fields.