BE 20.4 - 'reserve' 1 'concurrent operation' for DeDup to Tape

Hi everyone -

On a client's installation I have a problem with keeping 'duplicate DeDup-backup to Tape'-jobs running without waiting for ending of a 'VM-backup to DeDup'-job.
Active jobs:  B2DD-4,B2DD-5,DD2T-2 and B2DD-6 (3 x backup to DeDup-store and one duplicate to tape - in total 4 concurrent operations (but setup for max 3)).
When the job DD2T-2 has ended, the tape-storage is in-active until one of the backup-jobs has finished.
How do we configure BE's job-/queue-manager to 'always start next DD2T-job' when tape-storage (LTO) is idle and there are jobs waiting for this storage/device ?