I don't use WYSIWYG but I'm sure it is available there. Alternatively I have a plugin that does that.

I think you can just add a class to the text you want i.e. <span class="center"> some text </span>
Do you use the quicktags plugin?

Here is an image. It is easy to modify an existing plugin, which is what I did.

The tx buttons create divs that can be edited and are left, centre and right. the dL dR do float, which again I think you can add by class.

So the function is already there, just not obvious.

So for a whole post surround the content with a <div class>

I've attached my plugin for you to look at you can delete all the bits you don't want etc and add 'justify' etc.
So like others select the text, whole post or single character and click on the button. it will surround it with a div and the appropriate class. The exact formatting is in the css file.

The file is only for the My Bits line in the image, the Maths one is seperate.

• mytagsndivs_plugin.zip (6.3 KB)

@maggi Yes, the WYSIWYG editor has such buttons, as you can see here: https://b2evolution.net/man/post-contents-panel