I hope we're talking about the same thing: I'm referring to a Custom TitleBar; you mentioned ToolBar. We had started trying to use an embedded panel, but stretching did all directions, not just horizontally, which is what we want.
I've tried setting the PX_TITLEBARHDR_TEXT element to the picture we want, stretched it to the margins, and set it to "Centered (preserve aspect ratio)", but it doesn't seem to want to be repositioned.
We're currently using PxPlus 2018 (v15.10) with WindX on Linux.