Allows persistance storage in belts/rigs.

Reloading from belts/rigs work. Magazine with highest ammo count across inventory and belts/rigs storage is preferred. When there is a tie inventory is preferred. Used mag is placed back to where the new mag was taken from.
Optional: Always prefer belts/rigs storage. Takes mags from belts/rigs first even if there is a fuller one in inventory. When no suitable mag is in belts/rigs fallback to inventory.

Open-able either via context menu or MMB on the item. Drag and drop is supported if storage is not opened at the same time. When drag and drop fails item is returned to inventory. Belts/rigs cannot be placed inside of a belt/rig.

Tooltip shows stored items similar to nested items.

Storage size is determined by tier which is configurable via item value. 3 Tiers for each slot right now with editable tier thresholds and sizes.
Tier 1 is the minimal item value at which a belt or rig will have storage. If you set this to 1000 no item will have storage in base game because all are cheaper than 1000.
Tier 2 and tier 3 then allows you to have gradually better storage with better belts or rigs.
With tier 1 = 0, Tier 2 = 100 and Tier 3 = 400 for rigs:
every rig has at least tier 1 storage because we do tier 1 = 0. Every rig worth 100-399 will have tier 2 storage and 400+ is tier 3 storage.

Optionally:
Limit storage to item type: This will disallow all items by default. Specific item types can be allowed with the other [Lim] settings. You can activate more than one setting which allow item types into belts/rigs.
Rigs can allow: magazines, medicine, ammo or/and grenades
Belts can allow: medicine, ammo or/and grenades

Seems pretty stable but treat with caution and don't put your best items inside for now.