New in Delphi 11 is the ability to adjust the date and time simultaneously on the TDateTimePicker. This will allow you to edit a TDateTime with a single TDateTimePicker instead of two. See it in Action.
Newly added in Delphi 11 to TCustomComboBox are the AutoDropDownWidth and DropDownWidth properties. These are super helpful if you want to have long items visible in the drop-down window. Watch this to see them in action.
New in Delphi 11 is the EditMargins property on TCustomMemo. You will find this on TRichText and TCustomMemo (as well as their data-aware cousins). This allows you to define the left and right margins within a memo. Watch on YouTube.
New in Delphi 11 is the design-time previews of VCL styles. This is going to make it much easier to take advantage of styles within your applications and customise them on a per-control basis. Learn all about this new Delphi feature here.