Qt 6.11 is out! See what's new in the release
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qt Designer object position change when set another to visible or not
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The idea behind layouts is that they group widgets automatically as they resize. If you want an item to keep its position, you can disable the others with myWidget->setEnabled(false); instead of hiding it completely. You can also „fill“ the position of invisible widgets by e.g. an empty label, which is less elegant.