I cobbled together a lot of disparate notes on Google Scripts to send a summary email of the emails I had starred, so they could be followed up on, and to control the subscription list by a Google Sheet. Don't need it anymore, but in case someone does, it's at least a good place to start. NOTE: LOOK FOR and do TODOs.

Starred_Email_Digest.gs

// This didn't seem to work on its own; set trigger via Apps Script interface.
// ScriptApp.newTrigger('bottleTheStars').timeBased().everyWeeks(1).onWeekDay(ScriptApp.WeekDay.MONDAY).atHour(4)

function bottleTheStars() {

  const max = 20
  let noHtml = `Below are the ${ max } latest unresolved email threads (still starred).

The link should take you to a search that will contain the thread (and hopefully only that thread).
`
  let html = '<p>' + noHtml.replace(/\n/g, '<br />') + '</p><hr />'

  const emails = GmailApp.search("is:starred label:XXXX") // TODO: replace XXXX with your label
  const limit = emails.length > max ? max : emails.length

  let emailTo = [ 'Someone <*@gmail.com>' ] // TODO: Make this into a real address. It's the default (before Sheet entries).

  const sheetID = 'XXXX' // TODO: replace XXXX with your Sheet ID
  const ss = SpreadsheetApp.openById( sheetID )
  const emailsInSheet = ss.getSheets()[0].getRange('A1:A').getValues() // first column == email addresses

  emailsInSheet.forEach(cell => {

    emailTo.push( cell )
  })

  if ( limit == 0 ) {

    html = '<p>No emails found. Huzzah?!</p>'
  }

  for ( i=0; i < limit; i++ ) {

    if ( emails[ i ] ) {

      let thread = emails[ i ]

      let subj = '' + thread.getFirstMessageSubject().slice(0, 50)
      let sender = '' + thread.getMessages()[0].getFrom().split('<')[0]
      let firstDate = thread.getMessages()[0].getDate()
      let firstDateFormatted = Utilities.formatDate(firstDate, Session.getTimeZone(), 'MM/dd/yyyy')
      let lastDate = thread.getLastMessageDate()
      let lastDateFormatted = Utilities.formatDate(lastDate, Session.getTimeZone(), 'MM/dd/yyyy')
      // let link = thread.getPermalink() // DO NOT USE: only works for YOUR email, not shared across accounts
      // so, use search...
      let link = 'https://mail.google.com/mail/u/0/#search/'
          link += encodeURIComponent('after:' + Utilities.formatDate(firstDate, Session.getTimeZone(), 'yyyy/MM/dd'))
          link += '+'
          link += encodeURIComponent('from:"' + sender +'"') // TODO: Fix? This seems to sometimes generate string breaks.
          link += '+'
          link += encodeURIComponent( '"'+ subj + '"' ).split('%20').join('+')
      let body = thread.getMessages()[0].getPlainBody().replace(/\r?\n|\r/g, ' ').slice(0, 150)

      html += '<p style="margin: 1rem 0.5rem 1.25rem;"><b>"' + subj + '"</b> from ' + sender + '<br />'
      html += 'Started: ' + firstDateFormatted
      if ( firstDateFormatted !== lastDateFormatted ) {
        html += ' | Last response: ' + lastDateFormatted
      }
      if ( thread.getMessageCount() < 2 ) {
        html += ' | <b style="background-color:yellow; color:darkorange;">No response yet.</b>'
      }
      html += '<br />"' + body + '..."<br />' + link + '</p>'

      noHtml += '"' + subj + '" from ' + sender + '\n'
      noHtml += 'Sent in: ' + firstDateFormatted
      if ( firstDateFormatted !== lastDateFormatted ) {
        noHtml += ' | Last response: ' + lastDateFormatted
      }
      if ( thread.getMessageCount() < 2 ) {
        noHtml += ' | NO RESPONSE yet.'
      }
      noHtml += '\n"' + body + '..."\n' + link + '\n\n'
    }
  }

  html += '<hr /><p>This email automatically generated because you are on the project team. Contact administrator at the From address to remove.</p>'

  noHtml += '\n\nThis email automatically generated because you are on the project team. Contact administrator at the From address to remove.'

  GmailApp.sendEmail(emailTo.join(','), limit + ' emails to wrap up', noHtml, { 
    htmlBody: html 
  })

}