In Impress table, Tab goes to next cell and Shift+Tab goes to previous. Ctrl+tab behaves as tab, ever since OO. This is enhancement request for Ctrl+Tab to make a real tab. No need for duplicated behavior, and Ctr+tab would be like in MSO.
Usually, ctrl+tab jumps to the next page on a tab control (browser tabs, for example). And does it really make sense to create a new _column_ with ctrl+tab? How about rows? Ctrl+tab is used in Writer to insert a real tab into the cell. The command is available for customization, yet it results in an unclear focus. My take => WF.
Currently it is not possible to create a literal TAB character inside an Impress table. In PowerPoint Ctrl+Tab can be used for that, and in Writer tables too. Confirming with: Version: 7.2.0.0.alpha0+ (x64) / LibreOffice Community Build ID: 9c930c4f3109d123c0831d0fcecf9c8b32e5bbc7 CPU threads: 4; OS: Windows 10.0 Build 18363; UI render: Skia/Raster; VCL: win Locale: hu-HU (hu_HU); UI: en-US Calc: CL