UIs for GEGL-based filters should expose units selection where available
At least one GEGL operation, gegl:grid, has units metadata:
ui_meta ("unit", "pixel-distance")
However, the UI for it in GIMP doesn't expose units selection, which is a functional regression from the pre-GEGL version of the filter (which did provide units selection).
Please make GIMP render units selection combo box when the relevant metadata is available.