Note: Close tab is turned (for experiment) into a hiding button for a child window.

Teach Story: Initially mentioned Manual's tabs were stored as C-array, but... As you see... There are only 2 out of 3 tabs are ordinary. And I forgot that additional check-logic should be added for this case. As a result, first(topmost) Text input box disappeared on each Close tab switch in Realease build version. Probably u understand why ;), or at least guessing why. After this lesson I'm using STL containers whenever possible :) Since asserts aid very much 👍