As I went over in a previous post which I will link, dealing with having multiple of the same mod (and as others pointed out with Arcanes) is frustrating. This results in equipping the wrong version of a duplicate mod and presenting the problem of it being removed from builds when you trade one of the duplicates away. The mod station tells you which is the equipped one (thank you Voltage for that information) but not on what items each is equipped nor does the arsenal screen give you any info. Due to this, the only way to ensure you don't give yourself a future headache is to check back in your mod foundry for each duplicate mod you put on to ensure you put the right one on. Doing so is very frustrating as half my build making is checking back and searching for a mod in the foundry to avoid future problems. This goes doubly for Arcanes which have no proper indication of any equip state resulting in people keeping their arcane at lower ranks for trading to avoid a massive headache of unequipping an arcane on tons of builds.
Can we please get an indicator in the arsenal screen (and trade menu for Arcanes) which tells you which mods and arcanes are equipped elsewhere. This would make it so much easier to know which mod and arcane is my primary and thus which to equip and which not to.
Edit: An additional option (to improve future building( is code the game to always equip the duplicate that is equipped elsewhere so you have one prrimary version that always gets used and always trade one that isn't equipped if there are duplicates.