was thinking today it would be very handy to have circuit libraries as opposed to symbol libraries ( or convert circuit snippets into symbols) , I find these days I’m mainly reusing "stock " ( to me ) circuits and then adding new bits . I keep a few schematics called "Useful circuits " that I cut and paste from , but its not very structured
It’s a quite logical thing to want to have, and has been requested before, and some other EDA suites also have a similar feature. Often it can also be combined with a PCB layout of that section, so you can for example just pull a power supply sub schematic into your project, and the PCB layout for that power supply section is then also ready to be put on the PCB as a block.
There are plans to implement this in KiCad, but I don’t know in what version. Maybe in KiCad V7, maybe later.