Feature Request: Ability to Sync Branches from Non-Default Base Branch in GitHub Desktop

### The feature request

Hi GitHub Desktop Team,

I hope you’re doing well.

I wanted to share a usability concern and a feature request based on my current workflow while using GitHub Desktop.

### Current Workflow

I am working with a branching structure like this:

* `main`

* `abc` (created from main)

* `xyz` (created from abc)

I regularly keep the `abc` branch updated with `main` using the “Update from main” option available in GitHub Desktop.

### Challenge Faced

Now, for the `xyz` branch, I want to keep it in sync with its parent branch `abc`. However, when I switch to the `xyz` branch in GitHub Desktop, the only available option is “Update from main”.

This makes it difficult to directly sync `xyz` with `abc` using the UI, even though `xyz` was created from `abc`. While I understand this can be achieved using Git commands (merge/rebase), it breaks the simplicity and convenience that GitHub Desktop aims to provide.

### Feature Request

It would be extremely helpful if GitHub Desktop could support one of the following:

* Allow users to **select a branch to update from** (not just the default branch)
* Provide an option like **“Update from parent branch”**
* Or dynamically detect and suggest the **source branch (e.g., abc for xyz)**

### Why This Matters

* Many developers use layered feature branches in real-world workflows
* Reduces dependency on command line for basic operations
* Improves productivity and consistency within the UI
* Aligns better with how branches are actually used in practice

I believe this enhancement would significantly improve the developer experience for users who rely heavily on GitHub Desktop.

Thank you for building such a helpful tool, and I appreciate your consideration of this request.

Best regards,
Raj Bokade
+919833485172

### Proposed solution

Feature Request

It would be extremely helpful if GitHub Desktop could support one of the following:

Allow users to select a branch to update from (not just the default branch)

Provide an option like “Update from parent branch”

Or dynamically detect and suggest the source branch (e.g., abc for xyz)

### Additional context

_No response_