#set page(height: 200pt)
#let determine-highlight(location, body) = context {
    let footnote-counter = counter(footnote).at(location).first()
    let fill = none
    let transparency = none
    let rem = calc.rem(footnote-counter, 5)
    if rem == 1 {
        fill = blue
        transparency = 90%
    } else if rem == 2 {
        fill = green
        transparency = 70%
    } else if rem == 3 {
        fill = yellow
        transparency = 50%
    } else {
        fill = red
        transparency = 30%
    }

    highlight(fill: fill.transparentize(transparency), extent: 2pt, body) 
}

#show footnote: it => {
    set text(weight: 900)
    determine-highlight(it.location(), it.body)
}

#show footnote.entry: it => {
    determine-highlight(it.note.location(), it.note.body)
}


#lorem(5)
#footnote[Highlight one]

#lorem(5)
#footnote[Highlight two]

#lorem(5)
#footnote[Highlight three]

#lorem(5)
#footnote[Highlight four]

#set page(height: 80pt)
#let highlight-item(fill: red, body) = [#highlight(fill: fill, extent: 2pt, body) <showcase-highlight>]

#set page(footer-descent: -4pt, footer: context {
    let all-highlights = query(selector(<showcase-highlight>).before(here()))
    let highlights-on-page = all-highlights.filter(it => it.location().page() == here().page())

    set text(size: 0.8em) // Apply custom styling to the highlights in the 'footnote'
    highlights-on-page
        .map(it => link(it.location(), it)) // Additional example:  link back to the highlight in the text
        .join(h(1em))
})

#lorem(5)
#highlight-item(fill: blue.transparentize(90%))[Highlight one]

#lorem(5)
#highlight-item(fill: green.transparentize(70%))[Highlight two]

#lorem(5)
#highlight-item(fill: yellow.transparentize(50%))[Highlight three]

#lorem(5)
#highlight-item(fill: red.transparentize(30%))[Highlight four]

#lorem(5)
#highlight-item(fill: purple.transparentize(10%))[Highlight five]