You can't leave it on the FR screen, it will go back to round robin after 30 seconds. But you can leave it on the MIN or MAX screen and use those to manually control the feed rate. We don't generally recommend that, but if it is working for you, so be it I suppose.
One of the ideas for future features is the ability to set a "maximum fan speed", which would be used just for the kind of situation you describe.
The other option is to run the convection fan off a rheostat and then set your MAX to 14, MIN at 6 (or whatever you use) and then let the Coal-trol run normally in the round robin.
You can also use the manual fan control on the Coal-trol to manually set the fan speed. Goto the FSA screen and use the up and down buttons to change it to FSM ##. Select the speed you want and it will hold there. There is a safety feature which will kick the fan speed back to automatic control if the FR climbs above 60 for 60 minutes. But, when this happens you can just put the control back into manual fan speed mode. The safety feature is there to help make sure you don't burn too hot or, depending on fan location ont he stove, overhead it by running too slow with a hot stove body near by. If you are using an unusually low MAX setting, though, then you can pretty safely ignore that concern and bump it back to manual fan speed mode.
Unfortunately, by using MAX in this out of spec way (it is meant to define the maximum fire stoking rate for the control) the control has no way of knowing 14 is a low fire. To really satisfy this issue we'd have to add a new parameter where you could leave MIN and MAX set to define minimum stove fire and maximum stove fire, and then a new pseudo MAX setting that allows the user to artificially limit the FR, which would in turn limit how high the fan speed got. As an aside, we actually have this in one of our ideas for controlling overshooting, where the control will automatically manipulate a virtual FR ceiling based on if it detects overshoot or undershoot.