Hi @Anonymous,
To add four dropdown for filter purpose should possible, but I don't think multSelection would work.
To have multi-Selection save in Excel should work, but for searching, it would require the selected string in a proper order, in order to match the value stored in Excel.
Some examples here, to add a search which would work for all the area, try the search function:
Search(Table1, TextSearchBox1.Text, "Field1","Field2","Field3",...)
For dropdown, we could take use of the fitler function:
Formula should be:
Filter(Table1, Field1=Dropdown1.selected.value, Field2=Dropdown2.Selected.value,...)
the results of all formulas are combined with the And function.
Reference for the functions:
Filter,Search, and Lookup functions in PowerApps
For situation you described, it is recommended to create a single screen with each category in hierarchy.
For example, we could start from field 1, after Dropdown1 has been selected (with no Gallery), Navigate to screen2, with a gallery1 fitlered by Field1, then Dropdown2 with values from field2, once Dropdown2 has been selected, it would navigate to screen3, with gallery2 filtered by field2 and field1.
Formula for Gallery1 under screen2, the items property should be:
Filter(Table1, Field1 = dropdown1.selected.value)
Formula for Gallery2 under screen3, the items property should be:
Filter(Gallery1.allitems, field2 = Dropdown2.selected.value)
Gallery3 under screen4:
Filter(Gallery2.AllItems, field3=dropdown3.selected.value)
.....
Regards,
Michael