You can set in widget property
If you want to do choose Instruments from division then ENT and IVS should be shown in business unit drop-down so u have to do the following steps:
1. Go to business property widget
2. Open visibility and set ‘based on attribute value .
3. Select attribute in drop down attributes
4.Tick based attribute value and then click OK.
Above screenshot or example will help you ….
Might be this will be helpful.
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You are looking for the constrained by function. See documentation here: https://docs.mendix.com/refguide7/reference-selector
For some reason this explenations is only in the docs for Mx7 but it still is valid for Mx9.
You will need to create two entities, one for division and one for business unit and they need to have an association based on your business case, (looks like one Division can have many BusinessUnits, so one to many Division_BusinessUnit)
You enter the values in these two entities and then use these two entities for reference selector, where the second reference selector for BusinessUnits would have XPath constraint.