how to remove delete button in SwiftUI List rows when in Edit Mode?

There is a modifier for that, just add '.deleteDisabled(true)'. You can also pass a variable into it making the delete disabled conditionally.

Xcode 11.2, Swift 5.1 Just don't provide onDelete in List and there will be no Delete buttons

Here is example

import SwiftUI
import Combine

struct ContentView: View {
    @State private var objects = ["1", "2", "3"]

    var body: some View {
        NavigationView {
            List {
                ForEach(objects, id: \.self) { object in
                    Text("Row \(object)")
                }
                .onMove(perform: relocate)
            }
            .navigationBarItems(trailing: EditButton())
        }
    }

    func relocate(from source: IndexSet, to destination: Int) {
        objects.move(fromOffsets: source, toOffset: destination)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Alternate approach (with limitations)

struct ContentView: View {
    @State private var objects = ["1", "2", "3"]
    @Environment(\.editMode) var editMode

    var body: some View {
//        NavigationView {
        VStack {
            // !!!  A. using NavigationView instead of VStack above does not work,
            // !!!  because editMode is not updated and always .inactive
            // !!!  B. Also it does not work in Preview, but works in run-time
            EditButton()
            List {

                ForEach(objects, id: \.self) { object in
                    Text("Row \(object)")
                }
                .onMove(perform: relocate)
                .onDelete(perform: delete)
                .deleteDisabled(disableDelete)
            }
//                .navigationBarItems(trailing: EditButton())
        }
    }

    var disableDelete: Bool {
        if let mode = editMode?.wrappedValue, mode == .active {
            return true
        }
        return false
    }

    func relocate(from source: IndexSet, to destination: Int) {
        objects.move(fromOffsets: source, toOffset: destination)
    }

    func delete(from source: IndexSet?) {
        objects.remove(atOffsets: source!)
    }
}