Welcome back!

Aside from basic tanking guidelines (like this one from the previous exp) there are no levelin guides afaik. I also don't think that would be necessary because tanks have been very steamlined since ARR.

e.g. you only have 1 combo as PLD until you get Goring Blade in HW, and Rage of Halone simply gets a potency upgrade in form of Royal Authority after that.

There are no enmity combos anymore, just "combos", nor any other enmity skills or spells like Flash, those are gone. Instead you just have your tank stance (Iron Will), Provoke and Shirk. Tank stance doesn't reduce your outgoing damage anymore, that's why "Sword Oath" (your old DPS stance) has also been removed. Instead "Iron Will" just increases your enmity generated by 900% of your damage (x10 multiplier). Provoke now adds additional enmity (I think it was worth 2k potency enmity that also gets multiplied by your tank stance, up to 20k potency enmity). Shirk is a tool added with Stormblood and swifts 25% of your enmity on a target party member (commonly paired with a macro with <p> whereas p is the co-tank position in your party list.)

As for your current "tanking", just turn on tank stance and you're tanking. Just dps and circle through your mitigation CDs. If you play off-tank, just turn off your tank stance and keep dps-in', done.