If I take a simple empirical proposition (“there is a cup of tea on my desk”) I can verify the claim made by looking at my desk to see if there is indeed a cup of tea on my desk. At a further level of abstraction, if I take a scientific proposition (“there is a law such as gravity which operates universally”) I can verify the truth of the claim by assessing its universality. If I can find an exception to the supposedly universal law then I can take the claim to be verifiably false. If I can find no exception to the rule then I can feel methodologically confident in taking the claim to be verifiably true.

In virtue of what are metaphysical propositions true or false? Is there any way to verify them? What significance do the answers to these questions have for the status we accord metaphysical propositions?

Personal experience.

If your personal expereince is that reality exists only as you currently experience it, while ignoring the possibility and probability in change that occurs in evolution and experience then you can sit still in any moment and make assumptions about reality in truth.

Universal laws that support the beliefs of the majority or co-creation, are but reflections of focus or attention.
Having the greater majority of the entire world population based on its (at that time) current knowledge and experience, the proposition that the world was flat, didn't make it so.

In retrospect now (thanks for that Joesus) I would consider a metaphysical proposition to be a statement of identity. This identity was always implicit, it is known and eealt with as intuition, but has never as such been made explicit. The most basic metaphysical proposition is 'A = A'. Before the forumlation of A = A we tacitly unquestioninglyaccepted the identy of things with themselves. Yet we cannot say that formulating A = A was meaningless, it is in fact an enormous leap of insight which opens many questions about how we stand in the world.

Therein lies the function of metaphysical propositions. They make explicit the axioms which drive our being in the world. That formulation will allow further reflection on them.

Only reflection on the causes and the consequences of a certain attitude towards the world uncovered by a metaphysical proposition can assess the value of that proposition. A method of enquiry might be to assume the contrary of what the proposition claims.

They are not meaningless they are meaningful, only they make something explicit which is usually buried deep within the surface. It will take a scraping of layer after layer to unearth what they mean. It is like finding an archeological artifact. You will only know what it is and what function it had by examining their surroundings, their time and what has been build around it. So determining the truth and value of some metaphysical proposition takes digging, cutting to the heart of what it tries to tell us about the world.

This doesn't have to happen. We don't have to re-invent the wheel, only allow the heart to guide us to the truth that exists within, or under the layers.
The need to examine the layers is subjective. The belief that understanding requires sifting through the layers may lead to manufacturing more beliefs if the intellect still resides within the same box.
By moving awareness beyond all boxes subject experiences and their relative conclusions can be avoided for a much larger or omniscient perspective where layers may be realized at the point from where they are created without spending a lot of time in and amongst them.