MainActivity.kt

val tabs = tabLayout.getChildAt(0) as ViewGroup
for (i in 0 until tabs.childCount - 1) {
    val tab = tabs.getChildAt(i)
    val layoutParams = tab.layoutParams as LinearLayout.LayoutParams
    layoutParams.marginEnd = dpToPx(resources, 8f).toInt()
    layoutParams.marginStart = dpToPx(resources, 8f).toInt()
    tab.layoutParams = layoutParams
    tabLayout.requestLayout()
}