THtmlTreeView is not calculating available width for the text properly. It is adding the ellipses (...) incorrectly. This is difficult to explain, but as you horizontally scroll the THtmlTreeView, the width varies significantly. When all the way to the left, the text fills only about 3/4th of the panel. As you move the scrollbar right, more text is shown, sometimes too much.
View the video here:
THtmlTreeView 1.5.1.0
Delphi 10.3.1
Eric