Example of custom Insomnia plugin

main.js

const fs = require('fs');

function selectFileArg(args) {
    const variant = args[0];

    console.log("selectFileArg::variant", variant);

    const pos = Number.parseInt(variant.value.replaceAll(/[^\d]/gi, ""))

    return args[pos];
}

function selectFile(args) {
    return selectFileArg(args).value;
}

function isFilePresent(args) {
    const filePath = selectFile(args);

    return filePath?.length > 0 ?? false;
}

function w(value) {
    return {
        value
    }
}

module.exports.templateTags = [
    {
        name: 'fileTag',
        displayName: 'File Tag',
        description: 'Quick select one of file',
        disablePreview(args) {
            console.log("disablePreview", args);
            return !isFilePresent(args);
        },
        args: [
            {
                displayName: 'Variant',
                description: 'Which one?',
                defaultValue: 'file1',
                type: 'enum',
                options: [
                    {
                        displayName: 'File 1',
                        value: 'file1'
                    },
                    {
                        displayName: 'File 2',
                        value: 'file2'
                    },
                    {
                        displayName: 'File 3',
                        value: 'file3'
                    },
                    {
                        displayName: 'File 4',
                        value: 'file4'
                    },
                    {
                        displayName: 'File 5',
                        value: 'file5'
                    }
                ]
            },
            {
                displayName: 'Filename 1',
                type: 'file'
            },
            {
                displayName: 'Filename 2',
                type: 'file'
            },
            {
                displayName: 'Filename 3',
                type: 'file'
            },
            {
                displayName: 'Filename 4',
                type: 'file'
            },
            {
                displayName: 'Filename 5',
                type: 'file'
            }
        ],
        async run(_context, arg1, arg2, arg3, arg4, arg5) {
            const file = selectFileArg([w(arg1), w(arg2), w(arg3), w(arg4), w(arg5)]);

            console.log("run::arg#", arg1, arg2, arg3);

            if (!file) {
                throw Error("No file selected");
            }

            return fs.readFileSync(file.value, 'utf8');
        }
    }
]