Just a couple of points
You can use Personal subs and functions in another workbook's macros or the functions in in another workbook's worksheet, …
BUT the Personal subs and functions have to written general purpose enough
a. Proper use of ThisWorkbook and ActiveWorkbook
b. No hardcoding that will prevent use by another workbook
c. Probably a lot more
I keep my Personal.xlsm in my XLSTART folder (I prefer xlsm instead of xlsb)
1. You can directly call a Personal macro sub from Alt-F8 if it doesn't require parameters
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2. You can make it a Reference so that you do not need the "Personal.xlm!". A sub like this will take paramerters
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Option Explicit
Sub DefinedAsReference()
FilterOnSelection
End Sub
Sub NotDefinedAsReference()
Application.Run "personal.xlsm!FilterOnSelection"
End Sub
3. You can call a Personal function on the worksheet
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Edit -- 4. A lot of people will keep their 'toolkit' macros in Personal.xlsm so that they can call / use them on any open visible workbook
I'm sure others will have additional ideas