[GREENFOOT-843] Ability to view prompts for filled-in Stride slots

In Stride, when a slot is empty, there is usually a prompt-text shown. For some frames like var frames and if frames it's initially structural hints (e.g. "type"), but for method call frames it becomes contextual parameter names, which is particularly useful. But once you've filled in (or even started to fill in) the slot, the prompt can no longer be seen. We should investigate some sort of mechanism (Mouse-over? With modifier key? Keyboard shortcut?) to allow the user to see the prompts again.

---

Issue metadata

• Issue type: Bug
• Priority: Medium