In the edit comic feature, it is not possible to change the title picture once a comic was included in the library.
For example, if an unnecessary first page was deleted after the comic was included in the library, there is still the original first page as title picture in the library and can not be changed anymore.
Only if the comic is deleted from the library and loaded into the libryry again.

Anything else can be changed manually (authors ect.)

Adder: just saw that this should have been fixed with version 7.0, but it seems to be it is still not working.

There are a couple of arrows in the cover for choosing the right cover for your comic. Are you having any issues using them?

Yes the arrows.
When I try to change the cover for an untouched Comic, it works.

But:
I deleted first the cover page from the cbr file, saved it again.
Then opened up the comic in Yacreader and edited it. It still shows then the cover that was deleted.
When I go forward with the arrow, next page, then back with the arrow -> it shows the new cover.
When I save then, the original deleted cover turns up again.

Does this describe better what happens? Just found out.

Ok, thank you. I will try to fix it asap.