how set the wifi channel width

[penM]

I was able to use the ar9280 on opnsense in AP mode.
However, I found that the GUI screen does not allow me to set the bandwidth (20/40MHz) that the wifi uses for communication.
Because 802.11n always uses the 40MHz bandwidth,
In the case of overcrowded 2.4GHz, the communication may become unstable.
If you want to change the bandwidth only in the GUI screen, you can do so by specifying the WIFI operating standard (b/g/a), but you have to discard the operation in na/ng.
Would it be possible to switch between 20/40MHz from the GUI as in the following pfsense?
https://github.com/pfsense/pfsense/pull/4363
Thank you very much for your help.

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