In 3.4.X there was a pulldown for various tags and now it appears to be gone. So, for spoiler I guess you just need to type in the pre-fix and suffix by hand?

Thanks!

You can customize your editor and add the button.

To be more explanatory...

ACP -> Customization -> (Editor) Toolbars

Drag stuff from the bottom up to the top (move mouse over the buttons to see what they do)

There you go. I answered from mobile.

How does the button to create the spoiler look like?

4 hours ago, Che Paev said:

How does the button to create the spoiler look like?

looks like an eye.