Is there a way to disable resize feature on the left side of event?, and allow only right side.
You need to disable resizing using eventResizeHandling="Disabled" (https://api.daypilot.org/daypilot-scheduler-eventresizehandling/) and add an active area at the end with action: "ResizeEnd".
The following tutorial shows how to add the active area:
Sorry, instead of using eventResizeHandling="Disabled" you need to disable resizing in onBeforeEventRender:
args.data.resizeDisabled = true;