Enabling users to toggle more GUI elements
Recoll should allow users to simply, quickly, and easily toggle more GUI elements. This does not require a GUI designer, nor, frankly, even much thought whatsoever. It's "dead simple."
Many open source software projects suffer from poor GUIs because the engineers who volunteer their time to work on these projects are not very interested in GUIs. Nonetheless, enabling users to simply, quickly, and easily toggle GUI elements is neither a subtle nor a sophisticated concept. Rather it is a remarkably simple concept as is demonstrated in the images (screenshots) below which I took of Audacious (an open source audio player).
In case the menu bar were hidden, then, perhaps "right clicking" in the Recoll search box would show an option to make the menu bar visible.