Hi, as a freelance sound engineer: this looks decent. Is a logarithmic plot of the resulting curves out of scope? I always found it quite useful especially in combination with a spectrum analyzer.

Other than that: I found it somewhat confusing that your UI groups parameters by type of control (e.g. all frequencies first) instead of grouping them by EQ:

  Low Shelve
    Frequency
    Gain
    Q
  Bell 1
    Frequency
    Gain
    Q
  Bell 2
    Frequency
    Gain
    Q
  Bell 3
    Frequency
    Gain
    Q
  High Shelve
    Frequency
    Gain
    Q

You appear to have a topmost UI group called "Effect Parameters" maybe it makes sense to utilze these instead to group the EQs — so one of those per band? You could then add an enable button per EQ band as a neat and probably simple to implement feature (especially useful for beginners who haven't developed their ears as they can toggle the band off and on and hear what it is doing).

Other than that I would just miss High and Lowpass filters. Especially HP filters are a thing that are extremely useful for cleaning up mic rumble and unwanted proximity effect, bonus points for variable steepness (6/12/18/24 db/Oct). In my dialog mixing time there wasn't a single channel without a HP on it (except those who already had it baked in of course).

Since you have a L/R stereo mode maybe an alternative Mid/Side mode could be considered as well.

Another question: do you prevent EQ cramping?