Hi,
I am using Moodle 3.5
I want to "sort by course" by default in Timeline TAB of Course Overview Block.
An admin can set the default tab in Site Admin > Plugins > Blocks > Manage Blocks and edit the settings for the Course Overview block.
The setting 'Default tab' enables an administrator to specify the tab that will be displayed when a student first views their course overview. When returning to their course overview, the student's active tab is remembered.
See https://docs.moodle.org/35/en/Course_overview for more information.