Did you get this figured out. I am having the same issue. No options in the settings or in the mod options either.

To anyone currently having issues with getting this to work.
-You need to go into the options menu.
-Go to the mods tab.
-Scroll down to the "Proximity Inventory" section.
-Make sure the "Enable "Proximity Inventory" box is checked
-Once that is done, at the bottom are three buttons, "Back, Accept, Apply."
-You "NEED" to click the ""APPLY" button, if you don't, "NOTHING" will happen.
-Now exit the options menu and return back to the game.
-Finally press the number "1" key on the number pad "NOT" the number 1 that sits above the "Q" on your keyboard, it might take a second to activate but open the loot inventory and give it a moment and whatever you do, "DON'T" go bashing the button multiple times, that will turn it off.

I have tested this myself and it does work if you follow the instructions as listed. If you keep having trouble try unsubscribing and resubscribing and try following these instructions again.