Tixati v3.19 portable was the last version to have the up/down arrows on the scrollbars on my Windows 7 computers.  If for some reason this is a feature and not a bug then PLEASE, PLEASE make it an optional feature!

I concur. The new GUI framework shows numerous annoying limitations, and Tixati overall looks less eye-pleasing because it no longer integrates seamlessly with the rest of the system (like it did before). If the system theme is set to Windows Classic, Tixati 3.29 takes the colors, but makes all buttons flat instead of leaving the look for OS to decide on.

Users of the newer systems may also find some minor changes inconvenient, e.g. you can no longer disable all button icons like before.

There are scrollbar setting in the settings window.
settings-user interface-behavoir
scrolling options, press configure button