Activate the editor window that contains the AutoLISP expressions you want to place inside a region.
Select the expressions you want to place inside a region.
Right-click and choose Insert Region.
The selected AutoLISP expressions should now be placed between the two comments
;#region and
;#endregion which define the beginning and end of the region.
Optionally, add a meaningful description after the
;#region comment to identify the code within the region.