Highlight System draws configurable outlines around actors in your scene. Objects are grouped into categories and each category has its own color, edge width, wall visibility and distance fade. Everything is driven by one master Post Process material and two lightweight Blueprint components, so setup takes a few minutes and requires no C++.

Key features

•       Per-category outline color, with HDR intensity control.

•       Distance-compensated edge width, so outlines stay consistent near and far.

•       Optional see-through-walls mode, or highlight only when the object is visible.

•       Max highlight distance with a smooth fade-out range.

•       Add a new category by adding one enum entry and one row in a map.

•       Fully Blueprint-based; the master material is organized into labeled sections.

More detailed information here