Multiple Forms in 15 page

In iMIS 15 mater page, there is a form enclose the whole template. How can I insert other forms in to master page without damage the site? For example, a area of the template allow you to login or a area for search.

Has anyone change or modify 15 mater page? I have other challenages on doing so. Like change style of treeview (no documentation of this control properties).

Thanks.