Arend Messages: hard to enable implicit goals

[marat-rkh]

1. Open the editor and paste the following foo function:

2. Notice, it has an implicit goal, but it is not shown in the Arend Messages.
3. There is no easy way to enable it. One has to first replace it with an explicit one, enable implicit goals on the toolbar to get implicit goals displayed:

It would be better to have that button for implicit goals always available.