Hey could you try this :
in a first step you would need to collect all the HR names in a collection and than add the all value to it :
ClearCollect(colHRNames,Distinct(Datasource,HRNames));
Collect(colHRNames,{Value:"HR all"})
use the colHRNames Collection ad Datasource for your Dropdown
on your gallery you can now add an If statement:
If(Dropdown.selectedText.Value="All Hr",Datasource,Filter(Datasource, HRColumn= Dropdown.selectedText.Value))
Let me know if it helped you.
