Here’s the formula. Notice the underlined 1’s — if the emoji you picked are not displaying correctly — try increasing this number. There are two of them, so play around until the whole thing displays the correct progress bar.
format(slice("✅✅✅✅✅✅✅✅✅✅", 0, floor(prop("Progress") * 10) * **1**) + if(empty(prop("Progress")), "❌", if(prop("Progress") == 0, "❌", if(mod(prop("Progress") * 100, 10) == 0, "", if(mod(prop("Progress") * 100, 10) >= 5, "〰️", "❌")))) + format(slice("❌❌❌❌❌❌❌❌❌", 0, floor(10 - prop("Progress") * 10) * **1**) + " " + format(round(prop("Progress") * 100)) + "%"))