Looks like there is a new option for filters on SharePoint Online related to lists? I had previously created a permission level for read and would not allow users to create new list views. I then set the default list view to show only items created by the user. Now it appears by default you can edit these settings?
Based on your description, I understand that you want to only show items created by the user.
Here're some methods for you to choose.
1.Go to List settings -> Advanced Settings -> Item-level Permissions -> Read access -> Read items that were created by the user.
2.Edit current view -> Filter -> Created by is equal to [Me].
3.Select the Created by column -> Filter by.