There's a "subtitle" that appears under the main title in previews, etc. Sometimes called "summary". Example here:
nostr:note1tpa8uzj45l4m6jgu36spmegjd2gwk384zxvsf4d49uxyzmvqm7xq6ux4up
What do you mean by doesn't do subtitles?
Also I think nostr:npub12vkcxr0luzwp8e673v29eqjhrr7p9vqq8asav85swaepclllj09sylpugg has a long form editor, but you may need a premium membership or something for it.
There's a "subtitle" that appears under the main title in previews, etc. Sometimes called "summary". Example here:
nostr:note1tpa8uzj45l4m6jgu36spmegjd2gwk384zxvsf4d49uxyzmvqm7xq6ux4up
Ah gotcha, wow I'm surprised they don't support those.