Looking for a routine that would toggle a smart plug off then on again after a few minutes once a month
You’ll probably need to use WebCoRe for something like that. The automations in the new SmartThings app can only go up to once a week.
Webcore would be the best way.
An ugly alternative would be to get creative with virtual switches as a counter.
Have one virtual switch for each week out of 4. Then use an automation that turns on switch 1 if none are on, 2 if 1 is on, 3 if 2 is on and 4 if 3 is on. Then trigger your routine when all 4 are on and then then turn all 4 off again. Ugly but functional.