Conditional Required Field in SharePoint Online Library Validation Syntax Error

Question

Goal

I have a "Managed Services" Choice column with predefined choices displaying as Checkboxes (allow multiple selections). I want to make another column required based on the selection of the "Managed Services" dropdown.

I used Library Validation on a SharePoint Online List with the new experience enabled.

Problem

I can not Save my Validation Settings: The formula contains a syntax error or is not supported.

My Columns

Overview

Managed Services

Examples

If "Managed Services" equals "Managed Service für Client" set "Produkt Client" required

If "Managed Services" equals "Managed Service für Server" set "Produkt Server" required

What I have tried so far

=IF([Managed Services]="Managed Service für Client",IF(ISBLANK([Produkt Client]),FALSE,TRUE),TRUE)

Answer 1

This is a known issue with SharePoint formulas.

Multi-selection fields (Choice or Person/group or lookup) are not supported in SharePoint formulas.

If you are using SharePoint online modern experience, you have to customize the list form using Power Apps to apply validation for list form fields.