Tags. In the paper journal I write dates but if I create a section for a project, I add page number(s) of it to the alphabetical index at the start of the journal e.g. R: Renovation: 12-15, 25, 49-52. In the electronic journal I have a directory structure like ~/Journal/YYYY/MM/YYYY-MM-DD.md and use tags. Tags not a part of the Markdown but I use convention from Bear app.
