Not all columns that are supported in a table support the display of a quick view.

For the currency, no referential constraint is defined by the service. Hence, you need to make the following entry:
<Association Name="assoc_6D52161C1362D99A31996E5BB23202E8" sap:content-version="1">
<End Type="STTA_PROD_MAN.STTA_C_MP_ProductSalesDataType" Multiplicity="1" Role="FromRole_assoc_6D52161C1362D99A31996E5BB23202E8"/>
<End Type="STTA_PROD_MAN.I_CurrencyType" Multiplicity="0..1" Role="ToRole_assoc_6D52161C1362D99A31996E5BB23202E8"/>
<ReferentialConstraint>
<Principal Role="FromRole_assoc_6D52161C1362D99A31996E5BB23202E8">
<PropertyRef Name="Currency"/>
</Principal>
<Dependent Role="ToRole_assoc_6D52161C1362D99A31996E5BB23202E8">
<PropertyRef Name="Currency"/>
</Dependent>
</ReferentialConstraint>
</Association>
XML Annotation
<!-- QuickViewFacets annotation for Currency-->
<Annotations Target="STTA_PROD_MAN.STTA_C_MP_ProductSalesDataType/Currency">
<Annotation Term="Common.SemanticObject" String="EPMProduct"/>
</Annotations>
<Annotations Target="STTA_PROD_MAN.I_CurrencyType">
<Annotation Term="UI.QuickViewFacets">
<Collection>
<Record Type="UI.ReferenceFacet">
<PropertyValue Property="Target" AnnotationPath="@UI.FieldGroup#CurrencyQuickViewPOC_FieldGroup_1" />
</Record>
</Collection>
</Annotation>
<Annotation Term="UI.FieldGroup" Qualifier="CurrencyQuickViewPOC_FieldGroup_1">
<Record>
<PropertyValue Property="Data">
<Collection>
<Record Type="UI.DataField">
<PropertyValue Property="Label" String="Decimals" />
<PropertyValue Property="Value" Path="Decimals"/>
</Record>
<Record Type="UI.DataField">
<PropertyValue Property="Label" String="CurrencyISOCode" />
<PropertyValue Property="Value" Path="CurrencyISOCode"/>
</Record>
<Record Type="UI.DataField">
<PropertyValue Property="Label" String="AlternativeCurrencyKey" />
<PropertyValue Property="Value" Path="AlternativeCurrencyKey"/>
</Record>
</Collection>
</PropertyValue>
</Record>
</Annotation>
</Annotations>
ABAP CDS Annotation
annotate view STTA_C_MP_PRODUCTSALESDATA with {
@Consumption.semanticObject: 'EPMProduct'
currency;
}
annotate view I_CURRENCYTYPE with {
@UI.Facet: [
{
targetQualifier: 'CurrencyQuickViewPOC_FieldGroup_1',
type: #FIELDGROUP_REFERENCE,
purpose: #QUICK_VIEW
}
]
@UI.fieldGroup: [
{
label: 'Decimals',
value: 'DECIMALS',
type: #STANDARD,
position: 1 ,
qualifier: 'CurrencyQuickViewPOC_FieldGroup_1'
}
]
decimals;
@UI.fieldGroup: [
{
label: 'CurrencyISOCode',
value: 'CURRENCYISOCODE',
type: #STANDARD,
position: 2 ,
qualifier: 'CurrencyQuickViewPOC_FieldGroup_1'
}
]
currencyisocode;
@UI.fieldGroup: [
{
label: 'AlternativeCurrencyKey',
value: 'ALTERNATIVECURRENCYKEY',
type: #STANDARD,
position: 3 ,
qualifier: 'CurrencyQuickViewPOC_FieldGroup_1'
}
]
alternativecurrencykey;
}
CAP CDS Annotation
annotate STTA_PROD_MAN.STTA_C_MP_ProductSalesDataType with {
@Common.SemanticObject : 'EPMProduct'
Currency
};
annotate STTA_PROD_MAN.I_CurrencyType with @(
UI.QuickViewFacets : [
{
$Type : 'UI.ReferenceFacet',
Target : '@UI.FieldGroup#CurrencyQuickViewPOC_FieldGroup_1'
}
],
UI.FieldGroup #CurrencyQuickViewPOC_FieldGroup_1 : {
Data : [
{
$Type : 'UI.DataField',
Label : 'Decimals',
Value : Decimals
},
{
$Type : 'UI.DataField',
Label : 'CurrencyISOCode',
Value : CurrencyISOCode
},
{
$Type : 'UI.DataField',
Label : 'AlternativeCurrencyKey',
Value : AlternativeCurrencyKey
}
]
}
);