Need to add a menu to the subnav with a plugin

[steven s]

I'm looking to add a dropdown at the beginning of the subnav in the forum and CMS.
Probably the blog too. I have the html.

For the navbar I need to enter it in two places, one for those registered and one for guests.
It will be the first item in the bar.
Same in the CMS and blog.

I can hard code it all with no problem, but need to remember if I make a change in 1 place, I need to change it in 3 or places.

In vB3 I created a plugin that stored a variable.
The variable $mymenu in this case would be the html.
Then I'd hardcode $mymenu where I needed it and edit the plugin when necessary.

Another way I used to edit templates was find and replace.

I don't understand how to do it in vB4.
I've read a couple articles on how to use the new variables.
I just don't understand it.

Perhaps I can make a plugin that stores the html as in vB3?, I still don't understand how to use that variable in a template.

Any advice?