Resize scheduler cells by user?

Unfortunately, that is not supported.

OK, are there any plans to support it in the future?

It's not trivial and it has various implications - e.g. it can be either non-persistent or it would require a manual timeline. Also, it's necessary to take into account that the time header columns don't have to correspond to the grid cells and so on.

So it's not in the plan at the moment. If you'd like to discuss the possibility of sponsoring this feature, please contact sales@daypilot.org.

According to this demo (https://javascript.daypilot.org/demo/scheduler/cellwidth.html) it's possible to change the cell width on the fly. This is exactly what I meant but I would like to do it by resizing any of the row header cells. see this video please https://drive.google.com/file/d/155uezWpOBOmhWP-ttJa6Bp2crToPBAYX/view?usp=sharing

It might look like it's almost there but this demo redraws the whole Scheduler on cell size change. Unfortunately making it work with cell border dragging is not straightforward, as I mentioned.