If you find that the Gboard is either too big or too small on the Lenovo Tab P12, here's a simple way you can resize it.
Simply open up any app which has a search box facility, such as a web browser, or even settings. From there, tap in the search box and the Gboard should appear. Tap on the icon, which has the 4 squares, usually located on the left-hand side. You can then use the tabs located top, bottom, left and right to resize.