Unfortunately, we cannot sort the multichoice columns. Some workarounds:
For each choice, create a new "Yes/No" column. For example, if you have Red, Green, Blue choices, then create new three columns:
Name: Red, Type: Yes/No
Name: Green, Type: Yes/No
Name: Blue, Type: Yes/No
Then you can sort and filter by individual columns you have ...
You can set Item Level Permissions based on Column and Field values by using SharePoint Designer Workflow.
You could refer to the following article to learn more infomation:
How to Set SharePoint Item Level Permissions based on Column and Field Values
This is not recommended for large lists, but you want to set item level permissions using a Flow.
The basic Flow would be:
On item created or changed
if field X = confidential
run steps to set item-level permissions
Set list item-level permissions in SharePoint using Flow
In addition to Ganesh answer (Which I really appreciate that), I also found another way to automate this in Power Automate (MS Flow) as mentioned in this post (Thanks to Chelsea and Rohit):
Is there a way to stop editing an item when the approval status is pending in SP online list?
This gets a little tricky because the CSR cycle happens very early as a page is loading (it is rendering the contents of the page, after all), and making an AJAX request to SharePoint for additional data takes a while (in computer time), and it's very difficult to get the CSR process to wait for an asynchronous call to the server.
So usually, my approach (as ...