Impossible to extend/shorten slurs cross-system via keyboard

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

"Linear" objects (slurs, hairpins, cresc./dim. lines, 8vas) can be extended or reduced with shift+arrow.
For slurs, though, this function looks broken if the slur starts from a system and ends to the following.

1 - Input a slur on a note, which will extend to the following

2 - Extend it to the next notes with Shift+arrow: you can also reach the subsequent system

3 - Deselect (or esc, or just do something else on the score), and going back selecting the slur:

4 - It is now impossible to extend or reduce the slur, you will only able to move the first part, showing the handles:

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/1965ee41-eda6-458c-b009-1e117c6274f1

What is the latest version of MuseScore Studio where this issue is present?

4.5.2 and 4.6 alpha

Regression

I was unable to check

Operating system

Windows 11

Additional context

Please notice that any other cross-system linear object, when selected, will show handles only on the first part: nonetheless, Shift+arrow still allows you to extend or reduce the line

https://github.com/user-attachments/assets/3b4c0cb7-44b2-4e19-bcce-b8e431043905

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible