i personally use a trigger to place a row and wish to make use of the last produced id for implementing within the subsequent query.

how could i actually do this?

the code appears like:

IF (NEW.counter >= 100) THEN
INSERT INTO tagCategories (name, counter) VALUES ('unnamed', NEW.counter);
// here i want to have access to the above inserted id
UPDATE tagCategories2tagPairs SET tagCategoryId = <<ID_HERE>> WHERE tagPairId = OLD.id

Perhaps you have checked out LAST_INSERTED_ID()? But bear in mind:

Should you place multiple rows utilizing a single Place statement, LAST_Place_ID() returns the worthiness produced for that first placed row only.