Hi Christof,
We are unable to reproduce the issue 'Margin is not applied for MinimizedItems'. We have prepared a sample to apply margin for minimized items, In the sample we have edited the style of SfTileViewItem to set margin and specified a key, which is assigned to SfTileview 'ItemContainerStyle' property.
Please find the sample in below link,
If the problem persists, Please provide us more information to reproduce the reported problem. So that it will be helpful for us to provide you accurate solution.
Please let us know if you need any further assistance.
Regards,
Vignesh V