Use the Audiosoftware REAPER (60 Days free) to set Markers for your Soundfile.
Set the timeline unit to Seconds
and export the Markers to an .csv file.
Upload the csv file, give a name and convert the file to an Macro.
Download the 2 xml Files.
2. Copy the file with the Name xxx_macro on the USB Stick with the GrandMA3 Folder Structure into the Folder:
3. Import and execute the macro
Right click in the Macros Pool
It creates a sequence in the sequence pool with prepared cues for each Marker.
and creates a Timecodeshow with connections to the Sequence.