Question on 3rd party application and ToS.

[Risvertasashi]

Is the use of a 3rd party application specifically made for only pre-placing waymarks in game for a fight a bannable offense and against ToS?

All third party programs that interact with FFXIV are against the ToS. No matter how harmless they might seem.

Now in practice SE has kind of fight club rules going on. You won't get banned for using, for example, a parser if you never mention it in game/use it for self improvement. But even then, it's technically not allowed.

If you're curious about their detailed stance... https://www.youtube.com/watch?v=3-WXYg-S05U&t=370