With channel looping, you could make an entire project inside of a single pattern and later use “Split By Channels” to separate them at the end to arrange in the Playlist.
This left a lot of users wanting to stick with version 11, mainly because of the style of workflow this allowed for inside of the channel rack. Channel looping was unfortunately taken away when the new GUI from version 12 was introduced.
One of the most important features added to FL Studio 20.1, was actually a previous feature in FL Studio 11.