No custom installation since 3.6.6?

Hi all,

I need to customize client installation for example to change sync folder to an existing folder and some more.
Since 3.6.6 (Windows client) after connecting to server, logging in and closing browser window, the installation screen with customizing options just appears for a part of a second, then it vanishes and syncing (with default sync folder on C:) starts.
Is it a bug or am I doing something wrong ? Worked well in the past…

Thanks and best regards,