DBGlass

Having to manage and edit PostgreSQL databases using CLI-based tools is certainly not the most intuitive or easily achievable thing you can do with a computer.
This is where specialized database client-apps come into play. With a simplistic approach and boasting a user-friendly and modern-looking user interface, DBGlass is an Electron-based piece of software that allows you to edit and manage PostgreSQL content with no more than a few mouse clicks.

Does not require installation and works on the most popular OSes

Since it is based on the aforementioned, popular framework, you should know that this app can be run on all major operating systems like Windows, macOS and Linux.
Getting started with the app is hardly challenging as you only have to download the app, unzip its package and launch it via its designated executable file.

Simplistic yet modern-looking interface and intuitive workflow

As expected, upon first launch, you are prompted to enter a set of credentials, necessary for establishing the connection to any PostgreSQL database. You are bound to discover that its interface is neatly organized, with a table panel on left side of the main window and a useful lower toolbar.
Just like in the case of many other clients of this type, DBGlass makes it as straightforward as possible for you to modify tables, as well as to add, move, rename and remove columns.

Should be enough for handling most PostgreSQL databases

It is worth mentioning that you can choose between two view modes, appropriately named Content and Structure, accessible from the lower part of the main window. Also worth your while is the fact that this utility allows you to work with widgets that will streamline the workflow.
Before we conclude, please note that you are required to hit the 'Save' button if you want your modifications to stick and, once that happens, you will no longer be able to make use of the 'Undo' feature.

Well-balanced utility for editing PostgreSQL databases

All in all, if you are currently scouting for an application that can help you deal with basic PostgreSQL-related tasks and that works on all the key OSes out there, all while looking modern, then DBGlass surely deserves to be on your list of possible options.