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Cell A1 has a list of all values in Column H (SORT(UNIQUE(H2:H)) which is then used as a data validation drop down list. when you choose a value, QUERY(IMPORTRANGE()) pulls the values from the main inventory sheet.
In this sheet we use this formula:
=QUERY(IMPORTRANGE("https://docs.google.com/spreadsheets/d/1mYZ1DjmJMJkvFM50e_s2LCeDjk5rpIQpW1gG61cB2ps","All!A4:H"), "select * where Col8 ='"&A1&"'")