Is paving a parking lot outside the building boundary allowed?

Exceptions probably exist for subordinate eaves, but at 2.5m one can certainly no longer speak of that. So I would assume that this exceeds the limit. What does the neighbor have standing there? Either you do it officially (then the neighbor has to register setback areas on their property) or you agree on tacit tolerance and hope that the subsequent owner of the neighboring property sees it the same way.

What does the neighbor have standing there?

Also just a garage. Therefore, it doesn't bother him at all.

Either you do it officially (then the neighbor has to register setback areas on his property) or you agree on tacit consent and hope that the next owner of the neighboring property sees it the same way

Register setback areas on his property? In that case, it wouldn't apply with a garage on his side, would it?
Is "tacit consent" meant as a formal procedure or just a written confirmation between each other?

If you want to do the thing legally, then it causes an encroachment of setback areas on the neighbor's property. Of course, he is not allowed to build anything there. That is a disadvantage for him, and he probably won't just accept it like that. The alternative is to do the whole thing illegally. You regularly invite the neighbor over for a good bottle of wine, and he pretends not to have seen that the roof extension is one meter too long. As a neighbor, I would definitely not agree to anything in writing.

Now we would like to generously cover the entrance area and thus directly the entire area in front of the garage (garage width) with glass, preferably with a depth of 2-2.5m.

A canopy itself is probably "subordinate" as a "structure," but not as an "eaves overhang." Transparency or delicacy are not sufficiently weighty arguments to "pretend as if it were almost not there at all." I therefore see that it must endure the same restrictions as the structure it is "attached" to.

If you want to do it legally, then exceeding the setback areas on the neighbor's property triggers an issue. He then, of course, is not allowed to build anything there. That is a disadvantage for him and he probably won't just allow it.

Just for understanding: In this case, however, he wouldn't have a disadvantage, since my roofing would also directly adjoin his garage and thus the existing setback areas would actually not be affected!?

As a neighbor, I definitely wouldn't agree to anything in writing.

Hmm, why not, if basically no disadvantage arises? Because of possible "vulnerability" regarding cooperation? :)

A canopy in itself is probably "subordinate" as a "structure," but not as a "roof overhang." Transparency or delicacy are not sufficiently weighty arguments to "pretend as if it is hardly there at all." So I see it as having to accept the same restrictions as the structure it is "attached" to.

Of course, I understand what you mean, but I also try to take "proportionality" into account. After all, in practice it is naturally a difference whether it is a 0.5 - 1.0 m longer glass canopy or a longer building (garage or similar) that breaks the formal boundary...

Thanks anyway for your opinions.