"Add group" should additionally be a button "on hover"

[koppor]

Also for "All groups":

• The semantics of the button at "All groups" is "Add group"
• The semantics of the button at a group is "Add subgroup"

The plus symbol could be the one of the PR #9329.

The implementation needs to be differen.t

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Historic text:

(This is a duplicate of JabRef#529)

Other alternatives are listed in: #8398

[DumitruDruta]

I am working now on this issue. Can someone assign it to me.

[koppor]

I assigned you. Looking forward! I hope, JavaFX is manageable...

[DumitruDruta]

I created a draft pull request for the issue. I have not managed to implement the issue completely and I need some help with a couple of things that I mentioned in the pull request. Also for some reason not all the checks passed when I created the pull request, even though the code seems to run well on my machine, so I might need some support on that as well.

[koppor]

@DumitruDruta There was no activity in the PR, thus I think, this issue is free to take again. Interested contributors can see your changes and think what to do differently.

For questions regarding a PR, please ask at the PR itself.

I nevertheless reply here.

One can click on the red crosses on GitHub and scroll through the errors:

FAILURE: Build failed with an exception.

    org.jabref.config.rewrite.cleanup
        org.openrewrite.staticanalysis.UnnecessaryParentheses
These recipes would make changes to src/main/java/org/jabref/gui/groups/GroupTreeView.java:
    org.jabref.config.rewrite.cleanup
        org.openrewrite.staticanalysis.UnnecessaryParentheses
Report available:
    /home/runner/work/jabref/jabref/build/reports/rewrite/rewrite.patch
Run 'gradle rewriteRun' to apply the recipes.

> Task :rewriteDryRun FAILED
* What went wrong:
Execution failed for task ':rewriteDryRun'.
> java.lang.RuntimeException: Applying recipes would make changes. See logs for more details.

The text says

Run 'gradle rewriteRun' to apply the recipes.

This is possible on the local machine. That a code compiles is one part of the whole story, but it should also follow some code style rules, which are checked by OpenRewrite (and which also rewrites the code if instructed so).