Converting Metric working units - to Inches and Custom setting in the Settings Design File

Sorry if this is a repost, the site auto-deleted my first post and tagged it as spam.
Funny, first post in ages and I am a spammer. LOL

Anyhow...
Richard, yes this is do-able. However I think the macro recorder is leading you astray.
There may be a way to get it to record and do what you want, but my recommendation would be to do it the "hard" way.
Or in your case, will need to learn some new things, and use the Unit Definition methods.

The below code snippet should do what you are asking for.
Note that it appears you are requesting to change the file resolution from 10,000 units per meter to 100,000 units per inch.
Just make sure that is actually what you desire to do, as if you have any existing data in the file with any sort of real scale, the end result will be whacked and non-sensical. If file is empty, or the scale of existing elements don't matter, then OK.
Just pointing it out, as selecting the Edit button on the Advanced Settings button would warn you.
So the code below should give you exactly what you "asked" for, just make sure it is actually what you "wanted".

' ----------------------------------------------------------------------
Public Sub WorkingUnits_Inch_Tenth()
    Dim mu As MeasurementUnit
    Dim su As MeasurementUnit
    Dim uor As MeasurementUnit
    
    ' Set up DGN working units as:
    ' Define our desired Unit Of Resolution (UOR) as
    '   100,000 UOR per absolute storage unit (meter) and reflect in Inches
    ' Master Unit (MU) of Inches
    ' Sub Unit (SU) as One Tenth "TH" of an inch
    
    ' Create the unit definitions
    ' Note that all unit definitions are relative to metric standard
    ' So we define american units as conversion factors from meter
    
    ' First, define our desired UOR / Absolute Positional Unit
    ' relative to the standard Absolute Storage Unit of meter
    ' This is where the real magic happens and you are defining the
    ' conversion factor from 1 meter to your desired unit
    ' The stated goal was for UOR to be an inch
    ' 1 inch = 0.0254 meter
    With uor
        .System = msdMeasurementSystemEnglish
        .Label = ""
        .Base = msdMeasurementBaseMeter
        ' Units are stored as a fraction that will approximate the desired end result.
        ' Given 1 inch = 0.0254 meters, let's convert that to a fraction of a whole meter
        ' inches / meters = 1/0.0254 = Multiply to remove decimal (1/0.0254)*10000
        ' Provides desired result of 10000 / 254
        ' You can check yourself by doing the math and looking up official conversion.
        ' 1 meter = 39.3700787402 in , the result of the calculation is 39.37007874015748. Yup!
        .UnitsPerBaseNumerator = 10000#
        .UnitsPerBaseDenominator = 254#
    End With
    
    ' Now define our desired Master Units in Inches
    With mu
        .System = msdMeasurementSystemEnglish
        .Label = "IN"
        .Base = msdMeasurementBaseMeter
        ' Conveniently, in this case we want our Master Unit in Inches
        ' which in this case matches our desired definition of UORs in inches
        ' So we have the same values as above
        .UnitsPerBaseNumerator = 10000#
        .UnitsPerBaseDenominator = 254#
    End With
    
    ' Now define our desired sub unit of a Tenth of an inch
    With su
        .System = msdMeasurementSystemEnglish
        .Label = "TH"
        .Base = msdMeasurementBaseMeter
        ' Here we are wanting a result of 1/10 of above relative to UORS.
        ' We can accomplish this easily by multiplying the Numerator by 10
        .UnitsPerBaseNumerator = 100000#
        ' For inches, we want 254 like above, because this is now 254 * 1/10 of our MU
        ' it will result in 1/10 of an inch as desired
        .UnitsPerBaseDenominator = 254#
    End With
    
    
    'Now, we actually APPLY the desired unit changes we defined above
    With ActiveModelReference
        ' Define our desired Unit Of Resolution of 100,000 UORs per storage unit
        ' WARNING: Changing this value on existing files can totally whack your
        '  existing dimensions. It would have the effect of virtually scaling everything!
        ' So make sure this is really what you intend.
        .UORsPerStorageUnit = 100000
        
        'Now, we apply the UOR Storage Unit definition to translate
        ' from universal meter to our desired unit of Inch
        .StorageUnit = uor
        
        'Now, we apply our desired master and sub unit definitions
        .MasterUnit = mu
        .SubUnit = su
        
    End With
    
    ' Finally, desire to use coordinate format of MU:SU:PU
    ' This corresponds to global Coordinate Format setting of Working Units
    ActiveSettings.CoordinateFormat = msdWorkingUnits
    
    '  NOTE: Values are not stored permanently to design file until
    '   settings are saved.
    SaveSettings
    
End Sub
' ----------------------------------------------------------------------

Enjoy,
Gerald

SUPER, SUPER, THANK YOU so very much. I put your Macro 1st and than ran my 2 settings I already had and I get just what I wanted. I am so glad others can benefit from folks like you who know there stuff and take the time to share it. 

I so want to thank  - G -  or Mr. G, along with Jon Summers, and Jan and a few others along the way. Lorys Lee another great person of

knowledge and willing to assist so many. I had actually given up and thought I would never get it. Esp. when Leonard Jones said He did not think it could be done. So please accept the special thanks of this old fella who is trying to improve his speed at getting work done for my company and keep my productivity improving so I can keep a part-time job with LSI an Amazing company with such talent.

Thanks again to -G- and all who try to help this old bird keep his small income. (c8... God bless all

SUPER, SUPER, THANK YOU so very much. I put your Macro 1st and than ran my 2 settings I already had and I get just what I wanted. I am so glad others can benefit from folks like you who know there stuff and take the time to share it. 

I so want to thank  - G -  or Mr. G, along with Jon Summers, and Jan and a few others along the way. Lorys Lee another great person of

knowledge and willing to assist so many. I had actually given up and thought I would never get it. Esp. when Leonard Jones said He did not think it could be done. So please accept the special thanks of this old fella who is trying to improve his speed at getting work done for my company and keep my productivity improving so I can keep a part-time job with LSI an Amazing company with such talent.

Thanks again to -G- and all who try to help this old bird keep his small income. (c8... God bless all