Much like editing a shared word doc or spreadsheet you should be able to identify who else is in the same page/email/journey as you so you can either ask them to leave, or even have an admin remove them from that page. And have a way to track changes to the content in realtime.

For example if one user opens an email at 9am and then goes into a meeting for 3 hours, and in the meantime another colleague starts editing the email at 10am and finishes at 11am, the first user returns to the email at 12pm not knowing that someone else has been in the same document, and if they've made changes. They continue to edit the document and then save, overwriting all the edits the second colleague had made without either user knowing this had happened.

In word/excel you can see when another user is in the same file as you, we need this functionality in D365 too. And ideally the ability to refresh content to track changes made by others in realtime would be ideal.