Here are the changes that have been done so far:

Better support for sysinfo.dat and messinfo.dat - the dialog to load these files now has the correct filenames as default.

Removed Source Properties and Vector Properties options from game-context menu (when you right-click on a system name).

Removed Samples folder from Directories dropdown.

Removed HLSL tab. You can turn HLSL on from the Advanced tab. (see note* below)

Fixed the problem where you could not select software from the pick-list.

Fixed problem where the currently-loaded software wasn´t highlighted in the pick-list.

Fixed problem where the name of the software in the Device View was corrupted.

Slight speedup of loading data into the software picker.

The following are not supported and have been removed or deprecated:
sourcefile.ini
horizont.ini
vertical.ini
vector.ini
parent.ini
grandparent.ini
HLSL
Random Background
Samples
Broadcast
Mandatory cartslots

What still needs doing (if possible):

If more than one software is loaded, to make them all highlighted instead of one of them.

Enable to fill more than one slot from the pick-list.

Enable to unload one slot by using the pick-list.

Fix problem where all software is unloaded when you choose something from the pick-list.

If first-time run of a system, inherit file paths from its parent instead of from mess.ini.

*Currently HLSL crashes the system after you exit the emulation. It is hoped the cause can be tracked down soon.