Backup folder RegExp matches any leading .

[KlyithSA]

Options.vue line 30:
folderNameRegExp = /[\<\>\:\"\/\\\|\?\*\x00-\x1F]|^(?:aux|con|nul|prn|com\d|lpt\d)$|^\.+|\.+$/gi;

|^.+
This regexp matches any string with a leading '.' which is much more strict than needed for any sort of protection. Leading dots are totally valid Windows folder / file names. (There is an ancient protection in Explorer that prevents naming files with leading dots, but this is for user convenience only and can be bypassed.)

For linux users this is particularly annoying as it blocks the use of a hidden folder to keep extra clutter at bay.