As @Mirdarthos says Manjaro uses NetworkManager - ArchWiki
There are various different front-ends for NetworkManager, I gave nmcli commands because that’s simple but there is also nmtui which is a console-based gui, and most desktops will have some kind of integration (e.g. on KDE right-click the system tray applet and and “Configure Network Connections…”). It all does the same thing in the end which is change conf files in /etc/NetworkManager/.