In another universe, I got used to leaving myself short notes on a score as I worked on it - comments such as ‘from here’ (to remind me where to resume on starting my next session of work), ‘extra material to come here’ and suchlike. Dorico’s comments feature allows me to do this, but only if I click on my initials to see what each comment actually says. So I’ve taken to writing my notes using Shift-X, and making the font etc. distinctive enough to catch my eye when scrolling quickly (including putting it against a colourful background). This works well, but I can’t find a way of saving the format of my ‘notes’ as a custom text style which I can then access through the Shift-X dropdown. [How] can I do this?
You have to build it as a paragraph style in Engrave > Paragraph Styles, then use the star icon in the bottom left corner of the dialog to save as default.
Once you’ve done that, you can actually assign a key command (via Preferences > Key Commands) to call up specifically that Paragraph Style.
That said, are you overlooking the Comments section of the right panel, in Write mode?
Many thanks, pianoleo - much appreciated. As regards the Comments panel - yes, I have used it, but (unless I’ve misunderstood its possibilities) it can only show the text of the message as long as the panel is showing, and I normally work with as much screen space for the score as I can; so I find that double-clicking on my initials in the purple speech-bubble is better in those circumstances. However, neither does what I’d really like, which is something like this: 
So I’ll certainly follow the instructions you gave in your message, with thanks.
The solution you set out is exactly what I needed - many thanks, pianoleo.
Now that I’ve understood the basics of Paragraph Styles, could I ask another question about it? I’ve created a style that I want to appear as default below the staff rather than above it, and I can’t see an option for that in the Paragraph Styles dialog. Is it available elsewhere?
You can’t specify the default placement of text items as part of the paragraph style at the moment, I’m afraid.
Thanks for the speedy reply, Daniel.