Custom patch panel is not focusable

**Is your feature request related to a problem? Please describe.**
The `custom patch` panel is not _scrollable_ via keyboard, nor is it focusable via ``.

**Describe the solution you'd like**
Staging something to a custom patch should behave the same as partial staging, i.e. the panel should be focusable.

**Describe alternatives you've considered**
Using a mouse wheel to scroll through it does the trick.

**Additional context**
This is just a follow-up issue of a brief conversation on slack.