Luka,
Amungst other direct read/write functions from HD/FD, only the Master Folders of the HD can be directly accessed via the control panel of the SD1 (buttons such as the style buttons, sound/patter load etc). Other folders on board the HD and all in the FD have to be accessed via the regular DISK menu. Eg. the Sound Load button (found to the RHS of the screen) will take you directly to the Sounds folder on HD (Master Folder ON). However it won't take you to the FD, even if there were sounds on it). The design concept of the MASTER FOLDER was to ensure quick access to specific folders on HD. In your example (SINGLE REGISTERS, block registers, Midi files etc that reside on FD, files found in other HD folders but the MASTER FOLDER), you will have to access these via the DISK menu which will require SELECTING and LOADING.
Hope this helps.
AJ