DEVONthink uses Apple’s text editing code, which has no such command.
But there are kludges that may not be too inconvenient to use.
Type an extended row of underline characters to create a line. If you then copy it into the clipboard, it will be available to paste as many times as you wish.
Or copy an image of a horizontal line to the clipboard, for similar use.
I use the Snippets folder in XMenu for all manner of boilerplate text. Creating a text file (or .rtf of you want styled text) will allow you to insert something from the menubar pretty quickly.
Cheers!
(this line is courtesy of XMenu’s Snippets folder. )
Sadly, DevonThink provides no native MultiMarkdown support—a glaring gap in its feature set, especially given the number of excellent open-source frameworks that the devs could readily use—but you can use the excellent Marked.app (from the App Store) to convert MultiMarkdown into (formatted) HTML or RTF with at the press of a keyboard shortcut.
Thanks for the tips. The problem with those workarounds is that if the width of the page gets more narrow, then the line will be on two lines.
I found another interesting solution:
Slightly move the cursor down while clicking the mouse. A complete line will now be selected.
Choose a highlight color.
Change font size to 1 point.
Now the line is very fine and is always there as one single line, independent of the window width. And the cool thing is that I can copy/paste it too. Thanks for the tip with XMenu - I dragged a clipping of that 1 point line in there and it’s ready to be pasted. Works. Awesome!
However, I am perhaps picky, I don’t like those flashy colors and would prefer some sort of gray.
My question: How can I change the colors of the highlights?
OK, so I pasted that line (I had in an ugly purple) into a TextEdit document. I then selected it - wasn’t easy, only the 1 point line. So then I changed the color “Click to change the text background color” and dragged the line as a clipping into XMenu’s Snippets folder.