My Minibuffer and Completions in Tandem (mct) package is now available on GNU ELPA for Emacs version 28 or higher. You can install it with these commands:

M-x package-refresh-contents
M-x package-install RET mct

As I have demonstrated in a recent video, MCT is a very thin layer of interactivity on top of the default minibuffer and the standard *Completions* buffer. It basically adds commands to cycle between the minibuffer and the Completions, making the two work as parts of a unified space.

The package comes with a fully fledged Info manual. It provides a detailed overview of the functionality on offer, the customisation options, a sample configuration which also covers other useful built-in utilities (like file-name-shadow-mode), and more. Read the manual after you have installed the package by evaluating the following:

(info "(mct) Top")

Note that I just pushed a new tagged release: version 0.2.0. It improves a few things in the code base and expands the manual. Depending on when you install the package, expect an update to be available soon.