SharePoint List - Group items and leave one category open

You are right; the default "Group By" feature in SharePoint doesn't offer the ability to expand one specific group while keeping others collapsed. However, there's a workaround to achieve this using SharePoint's "Accordion" web part to display the list data in an expandable format.

Here's how you can do it:

Create your SharePoint list:

Go to your SharePoint site.
Click on "Site Contents" and then "New" to create a new list.
Enter the necessary columns and data for your list items.
Create a new page:

Click on "Site Pages" or the appropriate location where you want to add the new page.
Create a new page and give it an appropriate name.
Add the "Accordion" web part:

Edit the newly created page.
Click on the "+" icon to add a new web part.
Search for "Accordion" in the web part search bar.
Add the "Accordion" web part to the page.
Configure the "Accordion" web part:

Edit the web part and configure its settings.
For each accordion item, use the "Group By" value as the header and create a list view with the appropriate filter for that specific group.
Set the "Status" column as the grouping criterion, and in the filter section, specify "Status" equals "Error" for the item you want to be expanded.
Save and publish the page:

Save the changes to the page and publish it.
Now, when users visit the page, they will see the SharePoint list data displayed in an accordion format, with the "Error" group expanded, and the "Warning" and "Successful" groups collapsed by default.

Using the "Accordion" web part is a non-programmatic approach to achieve the desired result and doesn't require custom coding. It provides a user-friendly way to display the list data with the specific grouping and expanding behavior you mentioned.