Why doesn't the forum have insert code button like Q&A or like Unity forum?

It does. If you press the icon that looks like a quote symbol in the middle, there is a drop down for code. However, it doesn't work that well. It is better to use markdown. Just place 3 tildes (~~~) on a line by itself directly above and below the code and it will format it.

Well, it does work. But you have to properly have your pasted code highlighted first. Otherwise what it adds is formatting for inline code rather than

a code block
    formatting to 
    the multiple lines
    of text

Of course sometimes you do want it to be just a single inline code snippet.

I see okay. Markdown is more reliable for me, but I haven't messed with it too much.

It would be better if it was one button- insert code quotes is not what I think of as format- the Heading 1 Heading 2 puts me off from reading the rest. Even better would be the also have insert entire project button.

Does it add a scroll bar like Unity's insert code on its forum?

@cloa513 said: Even better would be the also have insert entire project button.

You can zip the project folder (on your OS) and drag the zip file into the comment box and it uploads.