Currently in Pro 3.1 if I have to do field based symbology, I have to select the column via drop down menu. I would like to request to add a search bar besides the drop down menu. A search bar can help in filtering the columns and also in quickly selecting a column in case there are a lot of columns. Like if the dataset has lots of columns then your mind kinda gets lost searching for the column through the long list drop down menu.
I would also recommend adding a similar field/column search bar in fields view, labeling class properties and the calculate field tool. Basically any tool/feature that allows field selection function should have the search bar functionality.