Reinstate value connection navigation positions

[microbit-robert]

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Description

Value connections are no longer navigable if they are empty. However, if you delete a block in this position, the cursor selects this value connection.

Value connections should be navigable if empty and this is a reasonable position at which to insert a block.

Reproduction steps

1. Go to the keyboard navigation plugin test page
2. Add an if block
3. Use the right arrow to move in
4. The value connection is skipped
5. Add a boolean to the value connection using keyboard controls, then delete it
6. The value connection is now selected, but there is no other way to get to it.

Stack trace

Screenshots

Screen.Recording.2025-05-20.at.12.23.10.mov

Browsers

No response

[maribethb]

Alternative: select the previous block when deleted instead of the previous block's next connection.

This is what I implemented in core and I think it works well and consistent with the rest of keyboard navigation

[cpcallen]

See also RaspberryPiFoundation/blockly-keyboard-experimentation#254

[kmcnaught]

I agree that the value connection positions are important. I know we now have heuristics and move mode that means it's not utterly essential to visit these locations, but losing this feels strange and I think users will want to navigate there. For example, the behaviour in this GIF looks very inconsistent to me: