replace.zs Contains the following:

// --- Simply Backpacks ---
//Uncommon
recipes.removeByRecipeName("simplybackpacks:uncommon");
recipes.addShaped("simplybackpacks_uncommon", <simplybackpacks:uncommonbackpack>, [[<minecraft:gold_ingot>, null ,<minecraft:gold_ingot>], [<ore:dyeYellow>, <simplybackpacks:commonbackpack>.marked('commonpack'), <ore:dyeYellow>], [<ore:chest>, <minecraft:gold_block>, <ore:chest>]], function(out, ins, cinfo) {var inTag = ins.commonpack.tag; return out.withTag(inTag);}, null);

//Rare
recipes.removeByRecipeName("simplybackpacks:rare");
recipes.addShaped("simplybackpacks_rare", <simplybackpacks:rarebackpack>, [[<minecraft:diamond>, null ,<minecraft:diamond>], [<ore:dyeBlue>, <simplybackpacks:uncommonbackpack>.marked('uncommonpack'), <ore:dyeBlue>], [<ore:chest>, <minecraft:diamond_block>, <ore:chest>]], function(out, ins, cinfo) {var inTag = ins.uncommonpack.tag; return out.withTag(inTag);}, null);

//Epic
recipes.removeByRecipeName("simplybackpacks:epic");
recipes.addShaped("simplybackpacks_epic", <simplybackpacks:epicbackpack>, [[<ore:dyeMagenta>, null ,<ore:dyeMagenta>], [<minecraft:iron_bars>, <simplybackpacks:rarebackpack>.marked('rarepack'), <minecraft:iron_bars>], [<ore:chest>, <minecraft:nether_star>, <ore:chest>]], function(out, ins, cinfo) {var inTag = ins.rarepack.tag; return out.withTag(inTag);}, null);
//--------------------------------------------------------------------------------------

Desired Result:

From the common backpack:
<simplybackpacks:commonbackpack>.withTag({inv: {Size: 18, Items: [{Slot: 0, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 1, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 2, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 3, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 4, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}]}, filter: {Size: 16, Items: []}})

To the uncommon backpack:
<simplybackpacks:uncommonbackpack>.withTag({inv: {Size: 33, Items: [{Slot: 0, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 1, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 2, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 3, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}, {Slot: 4, id: "minecraft:diamond", Count: 1 as byte, Damage: 0 as short}]}, filter: {Size: 16, Items: []}})