Please consider the following suggestions:
Dragging a bunch of instruments. Currently you can select a bunch of instruments, but you cannot drag this selection. Only one per time. This is misleading for intuitive work.
No instrument properties like tuning/semitone or volume cannot be changed for multiple selections of instruments. The common practice is the following from my experience: For example first instr. is tuned to “+1”, the second to 0. Now if you select both, a " * " or different box color will appear in the tuning/semitones box. If you move/switch up in the semitone box, a “+1” will appear, if you move down a “- 1”, until you unselect this selection of instruments. I the first case, instr. 1 has now “+ 2”, and instr. 2 has now “+ 1”. The same logic for other properties.
If you double-click on a empty area below the last instrument, a new empty instrument could be added.