Logic flow:

Input 1 -> original feed logic -> Stash block (no pop) -> Input 2 -> alternate feed logic -> Stash-pop block (mixes input 1 into 2) -> Remove Duplicates -> Sort by time


Source code:
{
    "displayName": "Test",
    "blocks": [
        {
            "id": "aaaont7hyzwjc",
            "type": "input",
            "inputType": "list",
            "listUri": "at://did:plc:p6aa3emrhidmw3ozqpirho35/app.bsky.graph.list/3l7uql36tk32v"
        },
        {
            "id": "aaaont7hy3iau",
            "type": "remove",
            "subject": "item",
            "value": "reply"
        },
        {
            "id": "aaaont7hyzlvy",
            "type": "regex",
            "value": "🦉 ",
            "caseSensitive": false
        },
        {
            "type": "stash",
            "action": "stash",
            "key": "w2yocra",
            "id": "aaaonua4w6ks6"
        },
        {
            "type": "input",
            "inputType": "list",
            "id": "aaaonus2nkwyo",
            "listUri": "at://did:plc:p6aa3emrhidmw3ozqpirho35/app.bsky.graph.list/3l7uqlbrnna2t"
        },
        {
            "type": "regex",
            "value": "🐍",
            "caseSensitive": false,
            "id": "aaaonvr3mukyk"
        },
        {
            "type": "remove",
            "subject": "item",
            "value": "reply",
            "id": "aaaonvkxtevtu"
        },
        {
            "type": "stash",
            "action": "pop",
            "key": "w2yocra",
            "id": "aaaonua4w6hqq"
        },
        {
            "type": "remove",
            "subject": "duplicates",
            "value": null,
            "id": "aaaonuheqry4o"
        },
        {
            "id": "aaaont7hyyaoa",
            "type": "sort",
            "sortType": "created_at"
        }
    ],
    "license": "EUPL-1.2"
}