Here is a summary of the main changes in v1.4.5. You can see the full changelog file here.

New lua interface

Lua scripting has been rewritten with a dedicated window for showing running scripts. Individual scripts can be enabled/disabled, and each script has its own context, so that functions/globals do not collide. A new callback system is present to allow multiple functions to be added to a single callback. Old scripts are still supported as being translated into the new system. Moreover, when users modify a running script, it is automatically refreshed.

Revamp settings

libTAS menus grow more and more, and it was getting difficult for users to navigate them. Most of the settings are now moved their own window with different tabs, while tools and common settings that you may change during the run are kept in the main menu.