For the Journal in my #plaintext #pim I use little different format. It's datetimestamp with `@` at the begining of line. Like '@ 2018-04-06 01:49'. Also, I manually put moth- and year- timestamps (with two and three `@` respectively). And, like with structure, I use script for navigation map generation and #vim folding for editing notes in Journal.
My inspiration for my #plaintext #pim was "Life inside one big text file" (AFAIK author abandon his system in favor of bunch of tiny text files under SVN version control). Later I understood that reopened system similar to Canon Cat of Jef Raskin. And third was article about Proteus notebook by Thomas Erikson.
At early days of my #lowtech #plaintext #pim there was only one all-in-one big file which was divided in two parts. Upper part was the Structure, the Lower part was the Journal - because this is naturally add notes one-by-one to end of file (like feed), and keep structured notes on top of file (like outline). As days goes by, a few global categories became sprouted and was splitted to separate files. https://mastodon.sdf.org/media/-Bvw-ff1A8PRhVkTCak
I use hybrid of #markdown and #asciidoctor markup with some asciiart for my #plaintext #pim and bare links for web content. At the beginning it was self-writed mapping for open web urls from #vim in #firefox, but later I discovered nice #vim shortcut - `gx`, which did the same job. Also change some scripts for getting title of web-page for second line of url (may be seen in screenshot), but that is another story. https://mastodon.sdf.org/media/2Jpde1Cv9dzPCEPzzHY