Waveform 11 CPU load/editing speed

[Jockomeister]

I am a new user of Waveform 11 and have not been happy with Midi editing speeds. For example, if I want to edit a note's velocity, there is a huge lag between clicking on the velocity tab, and then dragging it to the desired value, and then showing the new value. The task-in-process wheel shows up twice with each edit. I am using an older Mac Pro with four cores, but even so, cannot understand why editing a single velocity point should consume 5 seconds or more.

I have a CPU monitor running and it shows that Waveform is consuming more than 50% of my CPU activity when it is sitting open, but idle.

CPU load.png

Have I missed something in my settings? Any way to speed this up?
My Mac has 6 Gigs of memory, and all operating systems and applications boot from a 240 Gb SSD (which is at 50% capacity).

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Edit: I have discovered that it appears there is a lot of memory swapping going on, which is probably why my editing speed is so slow. So now I am wondering what is eating up all that memory? I am editing a midi string quartet and using some sf2 strings (one track each part) using Szforzando plugin. I've obviously got a setting wrong somewhere. Thanks for your help.