Hello & welcome !
However I cannot access scripts (there are some in the script subfolder, the .bas files can be seen on computer) - they are not displayed when I open the script folder from within CHDK.
Make sure the script files are stored on the "correct" partition of your card, i.e. on the partition holding your images, the "big" one.
With a partitioned SD card, the first ("small") partition is only used to start CHDK; after that, CHDK switches to the second "big" partition, this partition will be the correct place for all CHDK files and also your media files...
The length of the path / filename is also limited, using 8.3 ("MS DOS style") filenames is recommended.