This attached SplitView example is modified from from "fillItemOnLeft" autotest. Tested with Qt 6.4.0 it shows 2 potential issues:

1) Video 1: Initially the size of non-fill items grow bigger than SplitView, which follows documentation in the test:

// When the combined size of items is too large, the non-fill items should just exceed
// the size of the SplitView, exactly as they would were they in a RowLayout, for example.

But immediately when starting resizing the item shrinks to fit. I'm thinking content should be made to fit initially, while keeping inside min & max sizes. Or is there a reason for not doing that?

2) Video 2: When trying to move the left handle, middle area starts shrinking until right area reaches the implicitWidth.