Organ pedal marks

[PetJer]

Organ pedal marks implementation. Check out all the new features here.

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• I signed the CLA as PetJer:
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• Each commit's message describes its purpose and effects, and references the issue it resolves. If changes are extensive, there is a sequence of easily reviewable commits.
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[PetJer]

@igorkorsukov Can I already rebase this PR to use the new shortcuts system or should I wait?

[igorkorsukov]

@igorkorsukov Can I already rebase this PR to use the new shortcuts system or should I wait?

We decided to take it step by step rather than change everything at once.
The old shortcut system is currently working.
We're changing the internal interactions.
The new shortcut system is being developed in parallel and will be ready in 2-3 weeks.