KeY GUI slows down already at proofs of size 10000

[unp1]

## Description The proof tree rendering slows down for medium sized proof trees. ## Reproducible always ### Steps to reproduce > What is your expected behavior and what was the actual behavior? ### Additional information Problem is the tooltip rendering removing it resolves the problem, but we loose any nice proof tree label rendering, so a better solution is needed. --- * Commit:

[mattulbrich]

It seems that the tooltips on the proof tree (I assume the problem is about them) cannot be switched off at all. Would be nice if there was a tick box in the local menu to get rid of them tempoprarily ... @unp1