Select the destination of insertion in insert subsequence dialog

1. Open e.g. "_common_data/fasta/COI2.fa".
2. In appeared "Sequence reading options" dialog choose "As separate sequences in sequence viewer". Few sequences are displayed.
3. Click with right mouse button on empty space in annotation tree.
4. Go to "Edit sequence -> Insert subsequence..."
Current state: there is no any indication into which sequence the subsequence will be inserted.
Experimentally determined that insertion is carried into last focused sequence or in last one in list if there was no focus yet.