Indenting Child Rows for Large Data Sets

Hi All-- Really hope someone can point out a step I'm missing and this isn't lost functionality.

Sometimes I kick off large projects by importing a large data set from Excel and then build my project plan/ asset trackers by doing a manual workaround for indenting my parent/child rows. Here's what I've been doing:

1. I import the Excel file into Smartsheet.

2. I then filter out my header rows based on some kind of criteria so that I only show the detail lines.

3. I select all rows and indent.

4. Remove filter and voila-- all detail rows are now children of their respective header rows.

I've used this process MANY times before, but I'm trying to do this manual workaround now and it's not working. Suddenly, ALL rows are indenting including the rows that are filtered out. Was there a change that's preventing this? Or has anyone had success using this method that can help me figure out what I'm doing wrong?