Install bbrun by entering the following commands in the terminal:
sudo apt update sudo apt install bbrun
Description:
A tool for the blackbox/fluxbox window managers that runs commands
bbrun is a small but very useful application. It makes it convenient to quickly execute commands from the blackbox window manager. bbrun is very similar to KDE's Alt+F2 Run Command dialog box. When launched, it occupies a small portion of the desktop and docks itself to the right side of the screen. The run dialog is opened by clicking a tiny bbrun icon. . You don't necessarily need blackbox for this program to work. It looks just as good in fluxbox, but it won't look the same in other window managers.
Homepage: http://www.darkops.net/bbrun/
Version: 1.6-6.1build1
Section: universe/x11