100% this is necessary. It has been also a while ago in this thread.
https://community.smartsheet.com/discussion/108371/expand-collapse-by-one-step?_gl=1d24v65_gcl_auNzAwNTU1ODcwLjE3MTg1OTY3MDE._gaMTM0NTI5MTI5MC4xNjg4OTY5ODM5_ga_ZYH7XNXMZK*MTcyMjIyMjE5Ni45OC4xLjE3MjIyMjIyMTIuNDQuMC4w
Allowing child rows to be collapsed by default when opening a sheet would come a long way in improving the user experience. One of the downsides of Smartsheet compared to some of the competitors is that sheets can feel cluttered as they grow over time, mainly in cases where you have parent rows with a varying number of child rows. Multiple times I have found that a seemingly well designed project tracking sheet looks great at first, but once you add a significant number of projects and tasks to the sheet it becomes unpleasant to use. If I have to collapse 30 parent rows just to get to the one I am trying to view and edit, It makes me want to skip using Smartsheet altogether and just send an email to my team instead.