I have to customize the empty result message of a search result of a ValueHelpDialog. Is this possible somehow?

I have to customize the empty result message of a search result of a ValueHelpDialog. Is this possible somehow?

You could try fetching the table control via getTableAsync from the value help dialog:
this._oValueHelpDialog.getTableAsync().then(function (oTable) {
oTable.setNoData("No Data text"); // sap.ui.table.Table
});
API reference: sap.ui.comp.valuehelpdialog.ValueHelpDialog#getTableAsync