@C Rutherford I, too had a single in her 60’s year old tenant who spent the first year after I inherited her calling and texting, sometimes as many as 50 times per week.
I finally got fed up and told her by text and in person that if she was unhappy she could move. I followed this up with a text that stated she could continue to contact me for actual problems with the unit but that I would no longer be entertaining multiple contacts throughout the week about issues that had nothing to do with her unit.
The situation improved significantly after this.
I do still get texts about things that just really aren’t issues but I can usually deflect them with a short response.
As for the issue with the trash cans I try not to get involved in bickering between my tenants. Unless they are paying for their own trash by volume it doesn’t really matter whose trash goes where.
At times I have even suggested they call the police if they have significant issues with another tenant. This may not be the most ideal answer but for ridiculous things the police departments in my area will inform the tenants not to bother them and it usually ends the situation.