Can the box of multi line text in Microsoft List become larger? Easy to view

Roshan2023 Are you trying to increase the width of column in list form or list view?

 I think the screenshot you shared is from list form. In that case, check if you have applied any list form "body layout" customizations and remove those if any (it does not support single-column layout sections with full width currently).

Check this documentation: SharePoint list form - configure custom body with one or more sections 

Note: Configuring form body will switch your list or library form layout from single-column to a multi-column layout. We will add support for configuring the body with single-column layout in a future update.

As it is not possible using JSON formatting, you will have to customize the list form using Power Apps. Check: Customize a Microsoft Lists or SharePoint form by using Power Apps 

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