[FEATURE] Improve open-form by adding support for free form (non-enum) string multiselects

[nikcheerla]

Right now if you want to create a freeform string multiselect, you can't do it with the open-form API. You have to specify an enum.
I want users to be able to add a comma separated list of emails in a form but not have to select from a predetermined list

You could always have just a string input and parse it later by separating into commas, but this enforces less input validation and is worse UC

Could build a custom interactive modal, but feels like a use-case open form should just support

[zimeg]

Hey @nikcheerla! 👋 Thanks for sharing this feature request 🎁

I'm finding the same requirement that array inputs of a form need to include enum options. A quick exploration of the new dynamic options included with @slack/bolt seemed promising, but also did not work for me with form inputs.

At the moment the multi_select_menu block is most similar with an external data source, but I don't believe freeform input is accepted as arrays elsewhere 👁‍🗨

I'd recommend parsing a long string with either newlines or commas with the included "open form" step, as you suggest, but will also share this feedback with the team 💌

[zimeg]

Some more investigation surfaced the following page as the reference for external select options in a modal. AFAICT individual string inputs can be combined to form an array on submit, which might require multiple updates:

🔗 https://tools.slack.dev/deno-slack-sdk/guides/creating-an-interactive-modal

We don't have immediate plans to change select behaviors but sharing these suggestions to feedback@slack.com helps!