Hi.
Changing the "Auto Increment" value in the Operations part of phpMyAdmin would possibly do it. However I don't know it existing values for that field are not overwritten (= messing up the database!)?
E.g. 1, 2, 4, 5.
3 is missing. Set "Auto Increment" to 3 and create a new record. If the "Auto Increment" value then jumps to 4 or 6 ... don't know ...
... later ...
Changing the value makes MySQL put it back to the maximum (=6 in the example above). This method doesn't allow changing the cat_id manually.
Bye,