In addition to using the "lock" 🔒 button under Posts in selecting a default profile or lists (How do I lock a profile or list so it's always selected by default?), you can choose a profile or list as destination of your post in the composer.
In this article I will show you how to select a profile or list before creating a post.
Selecting a profile or list in the composer
(1) Go to Post Composer.
(2) Hover over the down arrow beside the name of the active profile/s. This will show you all your connected profiles.
(3) Click on "Lists" to show all the lists that you have created.
(4) If you want to set a profile or profiles as destination of your posts, click the box next to the profile name/s before creating your post. Make sure to click the "OK" button.
Notice that the selected profile/profiles will appear on top of the page in the "Posting to" section.
(5) If you want to set a list as destination of your posts, click on "Lists" then select the list where you want to send your posts to. Make sure to click the "OK" button.
Notice that the selected list will appear on top of the page in the "Posting to" section.