I've defined a Favourite Folder Format named 'test' and created a button set FORMAT=test,!folder (see below), but it seems to do nothing. Neither changes format to 'test', or to the format defined for a folder. Why?
OK, I solved it. Adding FF using Add to favourities RMB option adds a ff with all panels turned off. So essentialy after using the option, it is required to enable ff's features with Edit option.