I use horizon for all my schematics and it is very usable. The one thing that is not there yet is the coverage of the parts library, which is because all people involved only put parts into the official library if they have been approved by others. That means parts in that library are very unlikely to have mistakes, but it also slows down the process.
I ended up doing my own fork of the library while parts were still stuck in the PR process.
Still in active development. I still haven't gotten around to trying it, shame on me. Maybe I'll wait for Version H:
"What’s next
For quite some time now, people have been asking for hierarchical schematics. About equally as long, I’ve been thinking off-and-on about how to best go about implementing it. Once I made up my mind, I went ahead and implemented it over the course of about a month.
Even though the implementation is mostly done by now, I decided to not include it into this release so it receives some more testing by a wider audience. Apart from that, this results in version “H” bringing support for hierarchical schematics."
But it uses json for parts. So scraping and just writing it to your library is a real option, especially when you fall back on existing parts. It can also import parts from kicad, although I didn't try that.
I ended up doing my own fork of the library while parts were still stuck in the PR process.