XF 2.0 Insert another page (of a custom plugin) into the template

[canina]

I change one of the forums, and enter a list box change of select2, which receives dynamic data from the database.

I made a custom page that has inside this select2 box, but I want to know how you can insert this page into the forum templet.

I do not mind using a widget if that's the only option.

Thank you in advance for your attention