I think it's related to this error
Command failed: mvn -q help:effective-pom -Doutput=/var/folders/y9/d619hq154jb3fyl7b25dwfqw0000gn/T/exhort_uLI9iD/effective-pom.xml -f /var/folders/y9/d619hq154jb3fyl7b25dwfqw0000gn/T/exhort_uLI9iD/target-pom.xml

Which Maven extension do you use?

I feel like this is a duplicate of a known problem, but I cannot find the respective issue (maybe it was already closed). The issue has nothing to do with maven or really anything to do with the VS Code extension at all. When repopulating a plugin tree view, we don't store whether the nodes have already been expanded. Since expanding the tree node automatically attempts to fetch new results, the tree is reloaded and all data is discarded, leading to the observed behavior.

@tsmaeder Do you remember that issue?

@msujew sorry, no 🤷

Which Maven extension do you use?

built in Maven for Java v0.44.0 by vscjava

I seems that when we fetch the children of the "plugins" node, we get a onDidChangeTreeData notification from the plugin, causing a refresh of the tree root, which has the effect of collapsing all children. This looks like a bug in either our tree view plugins API implementation or our browser-side tree widget implementation.

@tsmaeder I believe that our tree widget system can handle this, as the explorer already does something similar. However, in the explorer, we only ever calculate a delta (i.e. which nodes to add) and not a full rebuild of the tree. Our tree view plugins API likely should cache all unaffected nodes instead of recomputing them.