iOS 14, `ScrollViewReader` + `TabView`, rough around the edges but you get the idea.

TilignTabView.swift

//
//  TilingTabView.swift
//
//
//  Created by Dan Tavares on 12/07/2020.
//

import SwiftUI

class State: ObservableObject {
	@Published var itemIndex: Int = 0
	@Published var color: Color = .white
}

struct TilingTabView: View {
	@StateObject var state = State()

	enum Options {
		static var animation = Animation.spring()
		static var pillColor = Color.black
		static var pillTitleColorSelected = Color.white
		static var pillTitleColorNormal = Color.black
		static var rows = [GridItem(.flexible())]
		static var scrollToPosition = UnitPoint.center
	}

	let items: [String] = [
		"Item 1",
		"Item 2",
		"Item 3",
		"Item 4",
		"Item 5",
		"Item 6",
		"Item 7"
	]

	func scrollTo(index: Int, scrollProxy: ScrollViewProxy) {
		scrollProxy.scrollTo(items[index], anchor: Options.scrollToPosition)
	}

	var body: some View {
		ZStack {
			state.color.edgesIgnoringSafeArea(.all)
			VStack {
				ScrollViewReader { scrollProxy in
					// Title Scroll View
					ScrollView(.horizontal, showsIndicators: false) {
						LazyHGrid(rows: Options.rows, alignment: .top) {
							ForEach(items.enumeratedArray(), id: \.element) { index, text in
								Button(action: {
									withAnimation(Options.animation) {
										state.itemIndex = index
										scrollTo(index: index, scrollProxy: scrollProxy)
									}
								}) {
									Text("\(text)")
										.bold()
										.foregroundColor(state.itemIndex == index ? Options.pillTitleColorSelected : Options.pillTitleColorNormal)
										.padding(.horizontal)
										.padding(.vertical, 8)
										.background(state.itemIndex == index ? Options.pillColor : Color.clear)
										.animation(Options.animation)
										.clipShape(Capsule())
								}
							}
						}
						.padding(.leading)
						.onReceive(state.$itemIndex) { index in
							withAnimation(Options.animation) {
								state.color = Color(
									hue: Double.random(in: 0...1),
									saturation: Double.random(in: 0...0.5),
									brightness: 1
								)
								scrollTo(index: index, scrollProxy: scrollProxy)
							}
						}
					}
					.fixedSize(horizontal: false, vertical: true)

					// Main Tabs Scrollview
					TabView(selection: $state.itemIndex) {
						ForEach(items.enumeratedArray(), id: \.element) { index, text in
							Text("\(text)")
								.font(.largeTitle)
								.tag(index)
						}
					}
					.tabViewStyle(PageTabViewStyle(indexDisplayMode: .never))
					Spacer()
				}
			}
		}
	}
}

extension Collection {
  func enumeratedArray() -> Array<(offset: Int, element: Self.Element)> {
	return Array(self.enumerated())
  }
}

struct TilingTabView_Previews: PreviewProvider {
	static var previews: some View {
		TilingTabView()
	}
}