Gaëtan raises the issue of an import of two libraries declaring levels that are unrelated (no constraints between them)
the proposed solution is to first Require the two libraries, then add the constraint between the levels, then Import the libraries to activate the parsing rules.
Discussion of the fact that the current parser supports several associativity rules at the same level, but usually this is not what we want.
Pierre may open an RFC and post it on Zulip to obtain more feedback.