This was an error which start in previous beta and made it way to the stable release. Unfortunately, you need to download the beta release to fix this problem.
This is beta version! It has not been tested.
Note: The wxWidgets update caused all kinds of issues so this probably isn't very stable build. Use with caution.
o Skin settings were not saved correctly if there were multiple instances of the same window active.
Post: Rainlendar 2.11 BETA build 121
But if you don't want to use a beta build, there is another way editing the config file, using this steps:
In your case, you need to find (e.g.):