Easy to use range loops

[djnotes]

There is some discussion in the issues about how bad the current loop controls are in LMMS, however I found nothing about how it should be. So, here's my one suggestion.

Enhancement Summary

Ablton and Ardour have nice looping options for each part of the track. In Ableton it is very easy; You select the part of the track you want to loop over using mouse and press Cmd + L (or Ctrl + L on PC maybe). This would be very nice addition to LMMS.
With regard to controls to do this, Ardour has Start and End loop markers that could be moved around thus setting loop points as desired. Ableton has loop controls with draggable ends, which is even more intuitive than Ardour.

Justification

The current looping in LMMS is a nightmare. Click here, click there, to finally set a loopable part of the track. Never really made sense how it works.

Mockup

Will add screenshots from Ableton.

[qnebra]

#6021

This could interested you.

[Spekular]

Dupe of #6014