I managed to find some info about the upnote://x-callback-url
scheme by looking at the source code to its Chrome web clipper. So here is an improved version:
#popclip - upnote v2
name: UpNote
icon: U
capture html: true
javascript: |
const article = {
html: popclip.input.html,
title: popclip.context.browserTitle,
url: popclip.context.browserUrl
}
const encoded = encodeURIComponent(JSON.stringify(article))
popclip.openUrl('upnote://x-callback-url/clipper?article=' + encoded)
(The above block is an extension snippet - select it to install the extension with PopClip)
Let me know if it works well for you.