When you’re using a plug-in in the Generic Editor UI mode, you must use the sliders to change values. This is because, although you can enter the values directly, if you do, the value goes to negative infinity.
Which plug-in are you talking exactly and which parameter, please? It works to me as expected here. I have tried internal Compressor plug-in, all parameters. I have tried Frequency, all parameters.
I just Switch to Generic Editor. Then double-click the value and type the value on the computer keyboard. Then I press Enter. Done.