How I Cross-Promote 18 Chrome Extensions Without Annoying Users

I publish Chrome extensions as a solo developer. I currently have 18 live extensions across two Chrome Web Store accounts, with more in development. Each extension runs in isolation. A user who installs ReadMark has no reason to know that Japanese Font Finder exists — unless I tell them. This is the cross-promotion problem. Done badly, cross-promotion is spammy: "You might also like..." banners competing with the actual UI, persistent notifications pushing other products, or promotional modals t