To do it with glide columns, you could create a Split Text column to split each part into an array. Create two single value columns to get the hour and minute values, then a template column to join it back together.
Might intially need a template column to lock the duration as a string before either method.
Also another method would be to use some mildly complex math to end up with 8.44 instead of 8:44:00, then replace ‘.’ with ‘:’
Maybe I should ask…do you only need the duration to be a string or does it have to be a number for further calculations?
I tried using Split Text column, separated the values by ‘:’
Used Slice Array to just get HH:MM and get rid of :SS.
Now the problem is, if the duration is 9 minutes 50 seconds lets say like shown in the screenshot in the last entry, the HH doesn’t show up at all. This would have worked if the HH:MM:SS column would have shown the duration as 00:09:50, instead it just shows up as 9:50. which invalidates our theory.