Logic's MCU control allows you to use the FLIP key to swap parameters like Pans, Sends and Plug-in Parameters to the UF1 fader.
You need to ensure UF1 is correctly configured to be able to control any plug-in parameter on the fader.
In the Mackie Control Setup page in Logic, ensure that Parameter Page Shift Mode is set to 'By One' (instead of 'By Page').
Once this is configured, you can press the PLUGIN soft key (Soft Key Bank 1, Key 3) to enter plug-in V-Pot mode and push on the appropriate V-Pot to start controlling one of your inserted plug-ins in Logic.
Press the FLIP key and then use the left and right cursor keys on UF1 to move through your plug-in parameters and get the desired one onto the fader to control.
For more information on PLUGIN mode, check out section 15:54 of our UF1+Logic tutorial.