SUMMARY When resizing a widget in the desktop edit mode and clicking/holding near the outer part of the resize handle circle the resize handles disappear while resizing a widget. STEPS TO REPRODUCE 1. Enter the desktop edit mode ("Customize Layout...") 2. Try to resize a widget (by clicking/holding near the outer part of the resize handle circle) OBSERVED RESULT The resize handles disappear. EXPECTED RESULT The resize handles stay visible while resizing widgets.
Can reproduce. It's a bit tricky, but I can do it if I follow the original Steps To Reproduce.
If I hover the cursor near the edge of the resize circle, the circle disappears, but the cursor is still displayed in its "resize" form. If I grab the resize circle by its edge (gotta click it fast, before it disappears), I can start the drag-to-resize operation, but if I wiggle the mouse around, it loses the grip as the resize circle eventually disappears during the resize operation, even though I'm still holding the left mouse button, that is pretty annoying. This feature is normally used only when setting up the desktop for the first time, so it doesn't affect much of everyday use. But since it is done on initial setup, it is perceived by first-timers and could pass a bad first impression about Plasma. I remember I saw it on my first day of use and it surely caused a bad impression for myself.
Cannot reproduce anymore in Plasma 6; seems fixed now, at least in 6.2, possibly earlier.