The idea of an autocomplete menu has been discussed previously in the Logos 6 forum and the essential idea reposted below and original post can be read at:
https://community.logos.com/forums/AddPost.aspx?ReplyToPostID=769004&Quote=False
In this discussion FL made the following comments:
Coincidentally, we are working on the spec for just such a contraption (though it may look a little different than your mockup since I don't know how much secret knowledge of each label type we'll be able to pump into the software, but we'll see).
Just such a specification exists. Now all we have to do is build it. 
This would make a significant inroads in improving the useabity of this aspect of the software which fits in with FL's current priorities:
https://community.logos.com/forums/p/136504/911405.aspx#911405
3. You think Logos is too complicated.
We have listened to you, and others, on these issues. We've made them three priorities to address this year.
We hear you. And we are working on it.
Making Logos easier.
We have some ideas for how Logos could actually guide you through a workflow, not just hand you a set of high-powered tools which you first have to learn how and when to use.
This suggestion helps guide a user through constructing a search query, the work had already been done on the specs. FL please make this as a part of your priorities.
Suggestion: create a visible add and click search editor (something like Syntax searching) where all the options (strings) for a search can be found. And links to help on the various strings. So that all is in one place.
Yes, I had the same thought.
I think it could be done fairly simply. (By that I mean simple for the user, not simple for the programmers. . What do you think, Eli?
My suggestion is that the { character triggers an autocomplete menu, just as the @ character does in a morph search.
Logos would then list all the search extensions. When you choose a search extension the menu would expand to suggest the appropriate attributes, and you can click the ones you want. Where users had to type specific information, Logos could either insert blanks or placeholders. It would look something like this:
The beauty of this suggestion (IMO!) is that it wouldn't add any clutter to the interface, and would be both simple and powerful. It may have some limitations (e.g. what if someone has hundreds of highlighting styles), but I think you could work around those by simply adding descriptive text to the suggestions, instead of every item from the list.
