How do i schedule a message?

There is no such feature as yet.

Apple Inc says; "We read all feedback carefully, but we are unable to respond to each submission individually."

Here is how for iPhone · Country or region* Select your country or region. · Feedback Type* Select feedback type. · Comments* Enter a comment.

Feedback - iPhone - Apple

You can create an automation in the Shortcut app that sends a message on a specific date and time.

1. Open the Shortcuts app.

2. Tap Automation at the bottom and select Create Personal Automation

3. Select Time of Day

4. Select the time the message should be sent and choose whether it should be repeated

5. Tap Next and select Send Message

6. Write the message in the "Messages" field, and the recipient in the "Recipients" field.

7. Tap Next, disable Ask Before Running if you want the message to be sent 100% automatically.

You can find more useful information here:

Create a new personal automation in Shortcuts on iPhone or iPad - Apple Support