To main problems.
1) It shows how many fields are visible, that information is not helpful 99.99% of the time you are looking to see how many fields you have hidden vs how many are showing. If you check your main competitor ie: Monday.com and Airtable the have the correct implementations. see attached file for examples.
2) When adding and removing field again you are using the wrong UI control as this control is apporiate in a different implementation. The biggest issue in using this control is it is not a checkbox or toggle switch so when adding and then redisplaying fields you have to remember the original position of the field because when your remove it from the display it then puts it at the bottom. See attached of how the main competitors have the correct implementation of this. Feel like the field picker was implement by a computer science intern who had no idea what he was doing.