TimerManager along with pretty much all of my submissions to the Helper Libraries and the Design Patterns are always going to be at a lower lever than what is proposed here. I focus on building blocks, not complete solutions. So I’m not surprised TimerManager doesn’t do what you are after. All it does it what’s in the name, manage separate Timers for individual Items, a common activity Rules developers need to achieve. What those Timers are for and what happens when they expire is outside the scope.
Without the code it’s really hard to provide any sort of feedback. I honestly couldn’t explain back to you what you are trying to accomplish and how it is distinct from Scott’s Mode library.
In general, I find that a lot of frameworks like these end up making it easier to reason about and use for the original developer but often do not make it easier for someone else to come along and use. It feels easier to reason about for you because you fully understand it and have already built up a model for how it works in your mind. New users will need to go through the effort of learning how it works from scratch and building up that mental model from scratch. Often that effort is a challenging as just coding it again themselves.
Whether that’s the case here or not I couldn’t say without looking at the code and figuring out how to use it.
See Design Pattern: Manual Trigger Detection for three approaches. Probably the most generic/fool proof approach is the No. 3, Proxy Items.