This would very helpful to have in systems where the game is putting its own color over sector squares (e.g. Dynamic Hive, Deneb). Currently you have to mouse over a sector on which you have a note in order to see what's there. All it would be is a menu button or hotkey to toggle them on or off.

Please be more specific. I can't tell what exactly you're wanting to see or where you're wanting to see it.

What do Deneb or Hive missions have to do with the suggestion?

Why should it be a toggle?

How should or would this affect the existing sector notes?

System notes block the colored grid squares on the system map. Deneb and Hive sectors that shade in those squares are overridden, and the only way to see them is to mouse over each specific sector to see if related text ("Currently occupied by a small Hive presence") shows up, rather than being able to visually see it on the map. It should be a toggle because I don't want to delete my notes or mouse over sectors in dynamic Hive systems to check for those sectors. It shouldn't affect existing notes at all, just make them not be shown on the system map.

From what I can tell, the sector notes aren't deleted when a there's a hive conflict in a sector, and I assume it's the same for Deneb. So, is the main issue here that the sector highlight doesn't indicate that there is a Hive/Deneb conflict in the sector.

Would it be sufficient if the conflict highlight superseded the sector notes highlight until the conflict was gone?
Does it need to be possible to switch back and forth between highlights?

I tried to make a last minute edit to my above post but wound up being too late.

I suppose I can see where toggling would be a useful feature. Perhaps there's one day where you want to focus on doing conflicts, but the rest of the time you don't want to be bothered by it. However, would you really be wanting to do something related to your sector notes if there's a conflict in that sector?

It would be more involved to implement, but it would be kind of cool if the navmap could display a split highlight for these occasions.

Having the conflict sectors override the notes would be the simplest "acceptable" solution, I agree. But as to your question "would you really be wanting to do something related to your sector notes if there's a conflict in that sector?" my answer would usually be no, but I can see having a lot of system notes and wanting to be able to check that I'm looking in the right area, even if I choose not to go there. Or maybe I really really want to mine a specific asteroid that's in a conflict sector despite the danger and now I'm mousing all over them.

+1 to either the original idea or conflict/"controlling" indicators superceding sector note colors

+1 Maybe one indicator could be as it is right now and another as coloured oultine aroud sector/grid?

Simple +1