Code tags, if you want to share something with tags that you don’t want to be parsed by the forum software:
<everything in in angled brackets is treated as a tag>, thus the angled brackets and the content disappear EXCEPT if you put backticks ( ` ) around it.
Cmd+Shift+C on the Mac, on Windows probably Ctrl+Shift+C.
Note: Apparently a comma, semi-colon, and exclamation or question mark break the angled brackets:
<lalala, ladeeda>
A line is created by typing three dashes aka hyphens (---) or underscores (___) in an empty line.
BUT if you put a dash directly under a text line, the text is turned into a headline.
(but you can get that also by beginning a line with the hash sign #), and there are seven levels of headers:
lala
lala
lala
lala
lala
lala
lala
# lala
## lala
### lala
### lala
#### lala
##### lala
###### lala
If you write two dashes (--) or three dashes (---) in a text line they are turned into an “En Dash” – or “Em Dash” —.
Likewise, if you type three periods (...) they are turned into the Ellipsis sign (…)
Bold and Italics / Italics are known, I assume.
**Bold** and *Italics* / _Italics_
Keyboard shortcuts: Cmd/Ctrl+B, Cmd/Ctrl+I
Numbered Lists?
- Just begin a line with “1.”, then you’ll see what happens.
- lalala
Bullet lists?
- Begin a line with a dash
- lala
There was more, but now I forgot what I wanted to add.
[a minute later] Ah, now I remember:
If you want to insert a link to a forum category, like #support, just enter a hash sign (#), and a list of categories appears:
<edit> finished the last sentence 
and changed the screenshot to dark theme.</edit>