VR Insert nesting?

Can I use VR Insert to add multiple items? If so, how?

For example, picture-in-picture and titles, multiple picture-in-pictures or titles in different locations, etc?

I tried layering a title over a picture-in-picture, but the title was hidden by the picture-in-picture.

Yes, this should be possible by stacking multiple copies of VR Insert. But the details may vary depending on which host you are using. You are a Vegas user, correct?

Yes, Vegas.

In Vegas the workflow for this currently requires the use of nested Vegas projects.
-Put the VR background clip on Track 1 and put the picture-in-picture in Track 2 below it.
-Apply VR Insert as a custom compositing mode on Track 1 and configure the insert as desired.
-Save this Vegas project as something sensible like InsertBackground
-Create a new Vegas project and import the InsertBackground.veg project as a media element and put it on Track 1.
-Put your title on Track 2 below it.
-Apply another copy of VR Insert as a custom compositing mode on Track 1
-Dial in the details on the placement of the second insert.

Update: Continuum 11.0.3 was just released (available for download from the Boris FX website) and it contains a simpler workflow for VR Insert in Vegas, particularly when stacking multiple insert layers. As of 11.0.3 you can apply VR Insert directly to the Text/Logo layers as a normal effect rather than having to use the special custom composite effect workflow.
-Put the insert layer(s) on the track(s) ABOVE the VR background.
-Apply VR Insert as a normal video effect to the insert layer.
-Let the host do the compositing over the VR background.

Here is a new tutorial showing the simplified VR Insert workflow in Vegas that was introduced in Continuum 11.0.3:
Use the VR Insert Filter to Composite Images into 360 VR Footage