AHA! Found the problem. I thought I had to put bp-custom.php in the root of the BuddyPress plugin folder, but it should go in the WordPress plugins folder instead! Now it’s working!
Just for good measure I completely swapped out the code I had in bp-custom.php and replaced it with the code you’ve proposed and still no success. Thanks for the help, though!
Sorry, the first few lines of my code apparently got cut off! I do actually have the define BP_DEFAULT_COMPONENT and tricks_change_bp_tag_position function in there. As far as I can tell I’m using exactly the same code that you’ve proposed. However, sadly, this hasn’t produced the effect I’m looking for.
Is there something else I should be including in bp-custom.php (aside from the opening/closing PHP brackets), or do I need to place bp-custom.php somewhere else other than the root of the Buddypress plugin folder?