Aquario RP70 “Mini” AM/FM/SSB Radio With NRC

[BC Coyote]

use main tuning knob to adjust?

It doesn't have a VFO function. It's a channelized radio, so that's not a "tuning knob" it's a selector with detents. It's possible that it does also function as a clarifier like you said, but if that's the case it must tune in steps. Hopefully they are tiny steps like 50 or 100 Hz.
Still a huge PITA. Dedicated clarifier control would be much better!

 

[Shadetree Mechanic]

In the picture, one of the digits on the radio display is underlined. This suggests that you can select which digit to manipulate.

 

[Crawdad]

In the picture, one of the digits on the radio display is underlined. This suggests that you can select which digit to manipulate.

Ala a Lincoln II and probably many others. VFO tuning via a rotary encoder.