How can I create a plugin that heavily modifies (or replaces) the default top navigation bar?

[bomalone123]

Currently, we are needing to add a second navbar right below the default top navbar, but we could replace it completely if that is simpler.

1) Is it possible to deactivate the default top navigation bar and replace it with something else by writing a plugin?

2) If not, is it possible to add a secondary navbar with additional links that can be styled with CSS?

3) If not that, then is it possible to at least add a secondary navbar simply with a few more links in it?

[pkirkeby]

You can add your own menu items to JIRA like this tutorial explains: https://developer.atlassian.com/display/JIRADEV/Plugin+Tutorial+-+Adding+your+own+Menu+Items+to+JIRA

[bomalone123]

No, not adding menu items per se, but replacing the entire bar with custom links and css.

EDIT: by using a plugin

[Hung Dinh]

What plugin do you use to replace the entirebar @Bo Malone?