Make changes quickly while staying in the context of a MR
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## Problem to solve
When working on an MR, our current UI makes it inefficient to make further changes to that MR. We can see some of that when users use workarounds to quickly make changes, like creating a suggestion and them applying that themselves.

There are also other ways, like making these changes in the Web IDE or their local IDE, but all of them require the user to move out of the context of what they were looking at in that moment.
## Target audience
- Sasha, Software Developer, https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas#sasha-software-developer
## Proposal
Find a way to make changes to the content of a MR without leaving the context.
### Permissions and Security
This should follow existing security.
### Documentation
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TBD
### What does success look like, and how can we measure that?
<!-- Define both the success metrics and acceptance criteria. Note that success metrics indicate the desired business outcomes, while acceptance criteria indicate when the solution is working correctly. If there is no way to measure success, link to an issue that will implement a way to measure this. -->
TBD
### Links / references
cc @jramsay
issue