You can use INFORMATION_SCHEMA.COLUMNS to check if the column exists or not.
CREATE TABLE t(rid int, foo int);
INSERT INTO t VALUES (1,1),(2,2),(3,3);
CREATE FUNCTION fnn(id int, new_val int) RETURNS void AS $$
IF NOT EXISTS(SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 't' AND COLUMN_NAME = 'bar') THEN
ALTER TABLE t
First of all, I don't think I would use that graphical visualizer tool in the first place. It seems to obfuscate more than it clarifies.
If you trace the "badge" down through the nodes to the bottom-most-one, it seems to correspond to this line from the text entry:
-> Bitmap Index Scan on usuarios_controllers_imeis_isn_tbl_id_usuario_controller_idx (...